5.3 and 5.4 – Salts (Grade 8)
1. Different uses of salts
Preserve food, table salt – to add flavors
Gymnasts use to keep their hands dry so that they do not slip on the
apparatus
Calcium sulfate
Make blackboard chalk
Aluminium sulfate
Added to dyes to help them stick to fibers
Copper sulfate
Soya seeds are coated with it. It stops fungi growing on the seeds
when they are planted
Ammonium nitrate
Used as fertilizer to help crops to grow well
2. All acids contain hydrogen
3. Name three COMMON acids that are found in the labs
Ans – Hydrochloric acid (HCl), Sulfuric acid (H2SO4) and Nitric acid (HNO3)
4. Name the other WEAK acids found in the lab
Ans – Carbonic acid (formed when carbon dioxide reacts with water)
Citric acid (found in fruits such as oranges and lemons).
5.
Name of acid
Salts formed from the acid Example of salt
Hydrochloric acid
Chlorides
Sodium chloride (NaCl)
Sulfuric acid
Sulfates
Copper sulfate (CuSO4)
Nitric acid
Nitrates
Potassium nitrate (KNO3)
Carbonic acid
Carbonates
Sodium Bicarbonate
(Baking Soda)
Citric acid
Citrates
Sodium citrate
6. Reactions:
Sodium Bicarbonate (Baking Soda):
Carbonic acid + Sodium hydroxide → Sodium bicarbonate + Water
H2CO3 + NaOH → NaHCO3 + H2O
Calcium Carbonate:
Carbonic acid + Calcium hydroxide → Calcium carbonate + Water
H2CO3 + Ca(OH)2→CaCO3 + 2H2O
Sodium chloride
Magnesium carbonate
Sodium Citrate:
Citric acid + Sodium hydroxide → Sodium citrate + Water
C6H8O7 + 3NaOH → Na3C6H5O7 + 3H2O
Calcium Citrate:
Citric acid + Calcium hydroxide → Calcium citrate + Water
C6H8O7 +3Ca(OH)2 → Ca3(C6H5O7)2 + 6H2O
7. What are the properties of acids?
Ans - Turning litmus red, turning universal indicator solution yellow or red, having a pH of less than 7, tasting
sour and that strong acids are corrosive
8. Name some everyday products that contain acids
Ans - vinegar, fruit juices, lemonade, fizzy drinks, citrus fruits, tomato and other savory sauces,
pickled vegetables.
9. Which elements are present in nitric acid?
Ans - hydrogen, nitrogen and oxygen
10. Which elements are present in the sulfuric acid? How many atoms of each element make up one
particle of sulfuric acid?
Ans - Hydrogen, sulfur and oxygen; two atoms of hydrogen, one atom of sulfur and four atoms of oxygen
1
11. What is similar about the formula for hydrochloric acid and the formula for sodium chloride?
Ans - Both formulae contain chlorine, Cl.
12. What is different about the two formulas?
Ans - The hydrochloric acid contains hydrogen, H, but the sodium chloride contains sodium, Na
13. Which ingredient is a salt?
2
Ans - sodium citrate
14. Do some researches to find out why this ingredient is added to some kinds of food?
Ans - Adding sodium citrate to foods such as orange jam helps to maintain its tangy taste and reduces the risk of
the product decaying.
15.
Different techniques of making salts
Reactants
Using
Metal + Acid
Products
Salt + Hydrogen
Using
Metal oxide +
Acid
Salt + Water
Using
Metal carbonates +
Acids
Salt + Water +
Carbon dioxide
By
Neutralisation
Acid + Base
Salt + Water
16. Examples of the above
Metal + Acid → Salt + Hydrogen
Zinc + hydrochloric acid → zinc chloride + hydrogen
Zn + 2HCl → ZnCl2 + H2
1. What is crystallization?
Ans - Crystallization is defined as a process by
which a chemical is converted from a liquid
solution into a solid crystalline state.
2. Write the word equation for this reaction?
zinc + sulfuric acid → zinc sulfate + hydrogen
3. What are the important practical points
you need to consider when you evaporate
this solution?
Ans - The solution may spit when heated, which
could cause burns.
4. Which do you think is the better way to
produce larger crystals – heating the
evaporating dish until there is very little
liquid left or leaving it to evaporate slowly?
Ans - Larger crystals will be produced when the
liquid is left to evaporate slowly, so that is the
better way.
5. How could you investigate which is the best
way to produce large crystals?
Ans – Using the same mass and volume of zinc and
acid for two reactions; using two identical evaporating
basins; heating one evaporating basin with a Bunsen
burner as in the experiment in the
Learner’s Book, leaving the other evaporating
basin so that the water evaporates very slowly,
and then comparing the size of the crystals.
Metal oxide + Acid → Salt + Water
Copper oxide + sulfuric acid → Copper sulfate + water
CuO + H2SO4 → CuSO4 + H2O
1. Make a list of the equipment you will need.
Ans - Safety glasses, 250 cm3 beaker, glass
stirring rod, copper oxide powder, dilute sulfuric
acid, measuring cylinder, filter funnel, filter
paper, conical flask, evaporating basin, tripod,
gauze, pipeclay triangle, heatproof mat, Bunsen
burner, tongs
2. Write a risk assessment for each stage of
the process.
Ans - The risk assessment should feature each
process, for example:
Step 1: Measuring acid and adding copper
oxide: risk of getting acid in your eye, so wear
safety glasses.
Step 2: Heating the copper oxide and sulfuric
acid: general risks of heating and not touching
hot items, wearing eye protection when using
acids, not boiling the mixture as harmful
fumes can be given off. Learners should
mention both the risks and how they can
attempt to overcome them.
Step 3: Allowing the mixture to cool: general
risks of heating and not touching hot items,
wearing eye protection when using acids.
Step 4: Filtering: risk of splashes of the
solution getting into the eyes, so wear safety
glasses.
Step 5: Evaporating: risk of solution spitting
and general risk of heating and not touching
hot items, using tongs to move the evaporating
basin, wearing safety glasses, taking care
about how close you get to the apparatus.
3. Suggest why the mixture was filtered
Ans - To remove any unreacted copper oxide
powder
4. Suggest how you could use a similar
method to make copper chloride.
Ans - Use hydrochloric acid instead of sulfuric
acid.
5. Write the word equation for the reaction to
make copper chloride from copper oxide
Ans - Copper oxide + hydrochloric acid → copper
chloride + water
6. Write the word equation for the reaction
between copper oxide and nitric acid
Ans - Copper oxide + nitric acid → copper nitrate
+ water
3
Metal carbonates + Acids → Salt + Water + Carbon dioxide
Calcium carbonate + sulfuric acid → Calcium sulfate + Water + Carbon dioxide
CaCO3 + H2SO4 → CaSO4 + H2O + CO2
Calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide
CaCO3 + HCl → CaCl2 + H2O + CO2
The rock LIMESTONE is made from calcium carbonate.
It is damaged when it reacts with acid rain and erodes (wears away).
The skeletons of coral are made from calcium carbonate and react with acids.
This happens when the oceans become slightly more acidic as more carbon dioxide dissolves in water
1. Read through the method and make a list of
all the equipment you will need
Ans - This will vary depending on what equipment
you have available but is likely to include
safety glasses, copper carbonate, hydrochloric
acid, measuring cylinder, beaker, spatula, filter
funnel, filter paper, conical flask, evaporating
basin, tripod, pipeclay triangle, Bunsen
burner, heatproof mat, tongs.
2. Carry out a risk assessment for each step of
the method
Ans - The risk assessment should feature each
process, for example:
Step 1: Measuring acid: risk of getting acid in
your eye, so protect yourself by wearing safety
glasses.
Step 2: Adding the copper carbonate to the
hydrochloric acid: wear eye protection when
using acids. The risk assessment should
feature each process and learners should
mention the risks and also how they can
attempt to overcome them.
Step 3: Adding excess copper carbonate: wear
eye protection when using acids.
Step 4: Filtering: risk of splashes getting into
the eyes, protection by wearing safety glasses.
Step 5: Evaporating: risk of solution spitting
and general risk of heating and not touching
hot items, using tongs to move the evaporating
basin, wearing eye protection, taking care
about how close you get to the apparatus.
Steps 6 and 7: low risk
3. What did you observe when you added
copper carbonate to the hydrochloric acid?
Ans - The most obvious will be bubbling as a gas
is given off.
4. Which gas is given off during this reaction?
Ans - carbon dioxide
5. Write the word equation for your reaction
4
Copper carbonate + hydrochloric acid →
copper chloride + water + carbon dioxide
6. Describe the appearance of the copper
chloride you have made
Ans - Any description should include colour (pale
green) and the nature of copper chloride
(crystals/powder).
7. Which substances in your word equation
are salts
Ans - copper carbonate and copper chloride
8. Using your observations from this
experiment, what can you say about the
solubility of copper carbonate and copper
chloride in hydrochloric acid?
Ans - Copper carbonate is not soluble as it is left
behind in the filter paper. Copper chloride is
soluble as it passes through the filter paper as
a solution
9. Suggest how you could use copper
carbonate to make copper sulfate
Ans - To make copper sulfate from copper
carbonate, the experiment could be repeated
but this time using sulfuric acid instead of
hydrochloric acid.
Acid + Base → Salt + Water
Sodium hydroxide + hydrochloric acid → sodium chloride + water
NaOH + HCl → NaCl + H2O
1. Carry out a risk assessment for each step of
the method
Step 1: Filling burette with acid: risk of
getting acid in your eye, so protect yourself by
wearing safety glasses; risk of spilling acid, so
use a small funnel and place burette at a level
lower than the bench to fill it; general risk of
breaking glassware.
Step 2: Measuring sodium hydroxide: risk of
splashing it in eyes, so wear safety glasses.
Step 3: Low risk
Step 4: Swirling acid around: risk of spilling
acid so take care, wear safety glasses.
Step 5 and 6: Low risk
Step 7: Filtering: risk of splashes of the
mixture getting into the eyes, protection by
wearing safety glasses.
Step 8: Evaporating: risk of solution spitting
and general risk of heating and not touching
hot items; using tongs to move the evaporating
basin; wearing safety glasses, taking care
about how close you get to the apparatus.
Steps 9 and 10: low risk
5
6
2. What colour is the universal indicator
solution in sodium hydroxide?
Ans - blue
3. What colour is the universal indicator in a
neutral solution?
Ans - green
4. Why do you need to swirl the flask as you
add the acid?
Ans - So that they mix together and react before
you add more acid.
5. Imagine that you accidently add too much
acid from the burette. What could you do to
form a neutral solution?
Ans - You could add a little more alkali until the
universal indicator solution turns green.
6. What salt is formed in this reaction?
Ans – sodium chloride
7. Write the word equation for this reaction
Ans – sodium hydroxide + hydrochloric acid →
sodium chloride + water + carbon dioxide
8. Describe the salt crystals you obtained
Ans - The description should include the colour
(white) and the shape of the crystals obtained
(cubic).
17. Which of the above compounds in Zn + 2HCl → ZnCl2 + H2 is a salt?
Ans – Zinc chloride
18. Which acid would you add to the metal magnesium to make the salt magnesium sulfate?
Ans – Sulfuric acid
19. Write the word equation for the reaction between iron and hydrochloric acid
Iron + hydrochloric acid → iron chloride + hydrogen
20. Why would it be dangerous to prepare sodium chloride by reacting sodium with hydrochloric acid?
Ans - Sodium is very reactive and the reaction would be explosive.
21. Write the word equation for the reaction between magnesium carbonate and nitric acid
Ans – Magnesium carbonate + nitric acid → Magnesium nitrate + water + carbon dioxide
22. Write the symbol equation for the reaction between magnesium carbonate and sulfuric acid
Ans – MgCO3 + H2SO4 → MgSO4 + H2O + CO2
23. How could you check that the gas given off in these reactions is carbon dioxide
Ans - By bubbling the gas through limewater, which will go cloudy if the gas is carbon dioxide.
24. The blue green colours in these rocks in the Atacama Desert in Chile tell you that they contain copper salts
This bright blue-green mineral in the tock is called malachite. It is made from copper carbonate
25. How can you test to see if a liquid is an acid or an alkali?
Ans - You could add an indicator such as universal indicator solution. If the test solution is an acid,
universal indicator solution will turn yellow or red. If the solution is an alkali, universal indicator solution will
turn blue or purple
26. What word is used to describe a solution that is neither acid nor alkali?
Ans - A neutral solution’
27. What are the properties of alkalis?
Ans - properties, such as soapy feel, turns litmus blue, turns universal indicator solution
blue or purple, has a pH greater than 7.
28. What is the difference between a base and an alkali?
Ans - A base is a metal oxide. Metal oxides are called BASES
SOLUBLE METAL BASES form alkalis when they dissolve in water
If a metal oxide dissolves in water, it makes and alkaline solution.
Example – Sodium oxide + water → sodium hydroxide
Sodium oxide is a BASE and sodium hydroxide is an ALKALI
29. Are all metal oxides soluble in water?
Ans - Some metal oxides are not soluble in water.
Eg. Iron and copper oxide are not soluble.
They do not form alkalis.
They react with acids to form salts.
30. Write the word equation for the reaction between magnesium oxide and sulfuric acid?
Ans – magnesium oxide + sulfuric acid → magnesium sulfate + water
31. Write the symbol equation for the reaction between magnesium oxide and sulfuric acid
Ans – MgO + H2SO4 → MgSO4 + H2O
32. Suggest how you could use iron oxide to make iron chloride?
Ans - Iron oxide could be reacted with hydrochloric acid to form iron chloride.
ROADMAPS
How to Determine whether a salt is soluble or insoluble in water?
7
In order to make life easier, chemists have divided salts into three types
Soluble Salts
Insoluble Salts
Potassium, Sodium and
Ammonium salts
8
1. What is the name of the indicator that is used to measure the pH of an acid or an alkali?
Ans – Universal indicator
2. How do metals react with acids?
Ans – They produce hydrogen and the metal salt
3. What is a 'pure' substance?
Ans – A substance which is made from the atoms of one element, or the molecules of just one compound. In
other words, pure substances are substances that contain only on type of particle.
4. What is evaporation
Ans – The process in which liquid turns into a gas water vapour( without boiling)
5. Calcium chloride is a salt that forms white crystals. It is used to absorb moisture from the air and is
known as a drying agent.
6. What is a carbonate?
The word 'carbonate' means that the chemical compound contains and oxygen linked together.
7. How to make crystals?
Ans – Step 1 - One way of making crystals in the preparation of salts is to start with a concentrated solution of a
substance.
Step 2 - When the concentrated solution is gently heated in an evaporating dish, the solvent begins to evaporate.
This causes the solution to become even more concentrated.
Step 3 - If the heat is removed and the concentrated solution is left to cool, evaporation will continue even
when it reaches the temperature in the laboratory. In time, all the solvent will evaporate and pure crystals of the
substance will be left behind
Step 4 - The pure salt crystals can then be dried by patting them gently and carefully with a paper towel.
8. What is a saturated solution?
Ans - A highly concentrated solution is called a saturated solution.
It is a solution that is so packed with a solute that no more will dissolve in it
9. Preparing a salt from a metal and an acid
Preparation of zinc chloride
Ans: 1. Small fragments of zinc are added to hydrochloric acid in a flask.
2. Bubbles of gas rise from the metal, pass through the liquid and escape into the air.
3. Eventually, the bubbles are no longer produced and some metal remains in the flask.
4. The contents of the flask are then poured onto filter paper in a filter funnel
5. The zinc metal remains behind and the liquid passes through and falls into a beaker.
6. The liquid is then poured into an evaporating dish and heated gently until some solid appears
7. The mixture is then left to cool, and more evaporation takes place until only the crystals are left behind
10. Why do you think that granulated zinc is used instead of a block?
Ans – It has a larger surface area and therefore reacts more rapidly.
11. What passed through the filter paper when the flask was emptied?
Ans – A solution on zinc chloride.
12. Why was the solution heated before it was left in an evaporating dish?
Ans – To speed up the process of removing the water by evaporation.
13. Write the word equation for this reaction.
Ans – Zinc + hydrochloric acid → zinc chloride + hydrogen
14. Here is the symbol equation for a reaction:
Zn + 2HCl→ ZnCl2 + H₂
What does this equation tell you about the reaction?
Ans – It tells us that when zinc reacts with hydrochloric acid, zinc chloride and hydrogen are produced.
15. Zinc sulfate can be prepared in a similar way. Write a word equation for the reaction.
Ans – Zinc + sulfuric acid → zinc sulfate + hydrogen
16. Here is the symbol equation for a reaction:
Zn + H₂SO₄ → ZnSO4 + H2
What does this equation tell you about the reaction?
Ans – When zinc and sulfuric acid are brought together, zinc sulfate and hydrogen are produced.
17. Write the word equations for the reactions between the following metals
a. magnesium and sulfuric acid
Ans – magnesium + sulfuric acid → magnesium sulfate + hydrogen
b. iron and nitric acid
Ans – iron + nitric acid → iron nitrate + hydrogen
c. calcium and hydrochloric acid
Ans – calcium + hydrochloric acid → calcium chloride + hydrogen
d. lead and sulfuric acid
Ans – lead + sulfuric acid → lead sulfate + hydrogen
e. aluminium and hydrochloric acid
Ans – aluminium + hydrochloric acid → aluminium chloride + hydrogen
f. tin and nitric acid
Ans – tin + nitric acid → tin nitrate + hydrogen
18. Preparing a salt from a metal carbonate and an acid
Preparation of calcium chloride
Ans. 1. The carbonate used in this reaction is calcium carbonate in the form of marble chips.
2. Some marble chips are added to hydrochloric acid in a flask.
3. Bubbles are produced and the chips dissolve.
4. Some more chips are added, and more bubbles are produced and then the reaction stops and some of the chips
are left in the solution.
5. Then the contents of the flask are poured onto a filter paper in a filter funnel and the solution and chips are
separated
6. The liquid is poured into an evaporating dish and heated until some solid appears.
7. The mixture is then left to cool, and more evaporation takes place.
8. When the mixture has been left to cool, it is filtered again.
19. Why did all the chips added at first dissolve?
Ans – There was an excess of acid to take part in the reaction with the calcium carbonate (marble) chips.
20. Why did some of the chips added later not dissolve?
Ans – All the acid had been used up so there was none left to react with the excess of marble chips
21. Why were the contents of the flask filtered?
Ans – To remove the solid from the liquid
22. Write the word equation for the reaction.
Ans – Calcium carbonate + hydrochloric acid → calcium chloride + carbon dioxide + water
23. A. Write the word equations for the reactions between the following metal carbonates and acids:
i.
zinc carbonate and sulfuric acid
Ans – zinc carbonate + sulfuric acid → zinc sulfate + carbon dioxide + water
ii.
aluminium carbonate and hydrochloric acid
Ans – aluminium carbonate + hydrochloric acid → aluminium chloride + carbon dioxide + water
iii.
magnesium carbonate and nitric acid
Ans – Magnesium carbonate + nitric acid → magnesium nitrate + carbon dioxide + water
iv.
copper carbonate and sulfuric acid
Ans – Copper carbonate + sulfuric acid → copper sulfate + carbon dioxide + water
v.
calcium carbonate and nitric acid
Ans – Calcium carbonate + nitric acid → calcium nitrate + carbon dioxide + water
vi.
lead carbonate and hydrochloric acid
Ans – Lead carbonate + hydrochloric acid → lead chloride + carbon dioxide + water
B. Here are three symbol equations for the reactions above. Match them with their word equations.
i.
Al2(CO3)3 + 6HCI → 2AICI3 + 3CO₂ + 3H2O
Ans - ii
ii.
CaCO3 + 2HNO3 → Ca(NO3)2 + CO2 + H2O
Ans - v
iii.
ZnCO3 + H₂SO₄ → ZnSO4 + CO2 + H2O
Ans - i
24. What is produced when you set up a reaction between a metal and an acid?
Ans – The metal salt and hydrogen
25. What is produced when you set up a reaction between a metal carbonate and an acid?
Ans – The metal salt, carbon dioxide and water
26. How would you filter a mixture of a solid and a liquid?
Ans - Fold a piece of filter paper to make a cone, and insert it into a filter funnel. Support the funnel above a
collecting vessel, and pour the mixture of solid and liquid into the paper cone.
27. Name two uses of calcium chloride.
Ans - It is used as a drying agent, in food processing and seasoning, in medicine and in speeding up the setting
of concrete.
28. Name four uses of zinc sulfate.
Ans - Cosmetics, some deodorants, making rayon fibres from cellulose, making glue, bleaching paper, in
making herbicides and sewage treatment, in chemical investigations.
29. Describe a crystal in one sentence.
Ans - A solid structure with flat sides.
30. You have a concentrated solution of copper sulfate. Describe the cystalisation process you would
use to make copper sulfate crystals.
Ans - The solution is placed in an evaporating dish and gently heated. The heat is then removed and the solution
is left in the laboratory, where it continues to lose water through the process of evaporation and the crystals
form.
31. Name all the equipment you would use to prepare a salt from an acid and a metal.
Ans - A spatula, conical flask, support (clamp and stand), filter funnel with filter paper in it, beaker,
evaporating dish, gauze, tripod, Bunsen burner, heat-proof mat used in the laboratory.
1
Link the name of the acid with its formula, and with the name of the salt it produces.
Draw lines to link the boxes. Use a ruler.
Acid
Formula
Salt
hydrochloric acid
HNO,
sulfates
sulfuric acid
HCI
nitrates
nitric acid
H,SO,
chlorides
2 The following compounds are all salts of sodium.
For each one, state which acid is used to make th¹ salt.
Sodium chloride Hydroch lonic,aad
Sodium nitrate
Sodium sulfate
3
Cnitric.acid
....
SulfurnC..accd
Write the name of the salt next to its formula.
NaCI
Sodium.chlortde.
Cuso,.Opper. sWtte.
Cucl, ..eppex..chloride
KNOJ..btassium.nitrate
4
Citric acid is found in fruit. What are salts of this acid called?
CiMates.
7.2Preparing copper chloride
This exercise relates to 7.3 Metal carbonates and acids from the Coursebook.
In this exercise, you explain the steps in the formation of a salt. You also consider safety
precautions needed when preparing a salt.
Sam and Elsa are preparing the salt copper chloride.
Sam pours some hydrochloric acid into a beake.
Then Elsa adds some copper carbonate.
copper carbonate
hydrochloric acid
1
What happens when Elsaadds theitgnate
copper
to the acid?
with
Elsa adds more and more copper carbonate until there is no more reaction.
There is some unreacted copper carbonate left in the beaker.
Sam filters the mixture.
filtrate
2
What is left in the filter paper?
..Cunreaed) coppec..canbonate
3 The filtrate passes through the filter paper into the flask. What is this liquid?
A.souton..f..LaRpea..chlarde..a..miatuaa".of..ate..md..cepper chlornd)
4 Next, Sam and El_a want to produce crystals of the salt. What must they do?
Elace.he.haiA..an..
cdesh. bad in...and.hed.it.to.exeporate
Cfhe.Qtend.easz.theCncfals.
5
Why must they be very careful when they carry out this step?
hihen.he..
6
Can..
What should they do to reduce the hazard?
Weam.sa4daea..preemamage.1ake..specua.cane ohennea.
exoporahag.shm...off.tha.heathen.aptn..bein.to..spit.
then.leare Uthe. .alatea..to.Naporate..inhe.....
7
Write the word equation for this reaction.
cpper
hydchloric
Coppor
Carbon dioxide
wter
Chlonde
aud
7.3Preparing potassium chloride
Carbonat
This exercise relates to 7.4 Forming salts by neutralisation from the Coursebook.
In this exercise, youdescribe the steps needed in some practical work to produce a salt from an
acid and an alkali.
Anna and Jon want to prepare the salt potassium chloride, using potassium hydroxide and hydrochloric acid.
1
hydrochloric
universal potassium
acid
indicator
hydroxide
For the first step in this process, Jon and Anna put 20 cm of potassium hydroxide in a beaker. They use the acid to neutralise it.
List the equipment that they need for this first step.
..Measwingcfldes,beakex,bunelte
niresat tndicatOI ADA
hydchloncacid
SaltyAtaeI
stand
Describe the method for carrying out this step. Include safety precautions.
Et..on..safy.glaasca.Eist..add.adop.of
.lactte..md..
How
olutien
wlach t4.e:Sel.uphe
4.,urdh.acid.
..mix the
potasium.hy.mxide....ancl..s..
3
wniverSa indi Cator
willJon and Anna know when the potassium hydroxide is neutrlised?
.MniNexIC.inciCator.olutuûn..hu..om.
blue to qreen
When the potassium hydroxide is neutralised, Anna and Jon have a coloured solution.
HÍw do they remove the colout, so that the, crystals of potassium chloride they prepare are pure?
the coour.
Ad..chaxcpaln..nesra.splutpnaka..M.
4 . L . ADkutiQn.dhpcld..be..teASA...e.mDS.h...pieceo.
5
Write the word equation for the neutralisation reaction.
Potasium. hydrchloric
potayium chlonce
aud
hydroide
oater
Rememnber
The general equation for a neutralisation reaction is
acid + alkali
6
’ salt + water
that
"0uton,
fametal
pxlde
in
uoate
LAntaun. hydroxialpaahdea.ia.he.oppota..of..an aud.
is an alkali?
Youmay need to
look up the meaning in
the Coursebook.
7 Potassium hydroxide is an alkali. Giye an example of another alkali.
Sodiu.m...hydaxicd.
What is abase?
9
..Metal.oxide
Potassium oxide is a base. Give an example of another base.
Lopper..Dxide
8.1 Investigating the reaction of calcium carbonate with an acid
This exercise relates to 8.1 Measuring the rate of reaction from the Coursebook.
Inthis exercise, youplot a graph of the volume of product obtained against time and interpret
this.
Anna and Nor investigate the reaction of calcium carbonate with sulfuric acid.
They use the apparatus shown here to measure the total volume of gas given off every 20 seconds.
acid
measuring cylinder
gas
water
conical flask
sulfuric
acid
1
lumps of
calcium
carbonate
What is the name of the gas given off, in the reaction?
Carbom...iDXIde
Here are the girls' results.
Time / seconds
Total volume of gas produced / cm²
20
200
40
350
60
450
80
520
100
560
120
580
140
580
160
580
2 Plot agraph of these results.
Time goes on
the x-axis.
Volume goes
on the yaxis.
Remember
Use most of the graph grid. Check your scales carefully.
produced/c
gos
of400
volume
500
3004
Total
(00
3
Nime fsecond lto
As.e..greAel.Mo...
uaents
no.maregs
aren af
Describe what the graph shows.
ihe..sIcepe,.tinae.faotta.
Suggest why no gas is given off after 120 seconds.
-Athe..calcium..catbontp.
Can..be.
pocuced
has
untll
20 seonde
akea comment.about
reacted
o..no.
moxCanbon
7.1 Investigating concentration
This challenge task relates to 7.4 Forming salts by neutralisation from the Coursebook.
In this challenge task, you will discuss variables in an investigation and make some conclusions
from experimental results.
Elsa was asked to investigate this question:
Is therea link between the concentration of acidand the volume of it needed to neutralise 50 cm of alkali?
She made up five samples of acid with different concentrations, 100 cm of each.
The first sample was from the laboratory bottle of acid.
The second sample was made by adding 50 cm of acid to 50 cm water.
Each subsequent sample of acid was half the concentration of the previous one.
burette
acid
For each sample, Elsa put the acid in a burette and gradually added it to the alkali, until a neutral solution was formed.
alkali
1 How could Elsa determine the pH of the solution, and what would _he observe as it became neutral?
lSa.GeA.CQuld.lAl..ùvaa..ndi,sato..sLAldion.hi.would..he.bue..calr
un..caSalne. aAtiAm....amd.AQLAld.he.9xeem..cOlOrhenneutralsed
2 Which variables should Elsa have controlled to make this a fair test? State at least three.
the
Same.ype,..of..acid..Same.ype.aQnd.conceghatuon...o4UkaiL.
alkali
..CAAMe...MLMe.0f
3
Samme...e.A...Jnix.Áal..I0dsato
Here are the results of Elsa's investigation.
Acid
sample
Volume of laboratory acid used to make up 100 cm|Volume of acid sample needed to
neutralise alkali / cm3
diluted sample / cm
100
21
50
25
25
34
D
12.5
51
E
6.25
100
B
auslcn
Sample A is the most concentrated and sample E is the least concentrated.
neutalhe
to
tuoed
Sot
aid40t
of
B0
20
Volume
30
40
S0
60
?0 30
90
00
Velume of lab oúd
wmd to mate gcmpt /cm
4
Describe the graph.
Jhe cmalleot oume
...alA..
5 What conclusion can you make from thes results?
Iha...atc.ta..Dncenhaa.Of.qs AAds.ttae.Small..ot. JAume..e
MceacaalieealgiAchcng.i.nanfraton,
-a..LA.AnCAnAtien.ha..MAs...
.Qn..h
R..af.t..ncedcd.
6
Elsa's results were for 50 cm3 of alkali.
Nor did the same investigation but made a mistake. She used 60 cm? of alkali.
How would Nor's results be affected?
Ih...eaulta..lel.be..csAxcat...a.ralen.yoME. ol a d wold be
.ne.edea.0..neutYadiSCtiQn..a..e.4c...NGAntaan..buIha..patten.
he..alutnG..faced..nGed.ed..4,lae..n.LcA.ntratuon..a.chamged...eud..
-be.naLtahed.graph.CAnMe.A.b...gh,ca,p..
oume
4nddescribe COnienhtcoM
the safety
State the dangers
should be taken. aud needed to
.LonceAtas.CAsaA...nAe.
asive.a.g
....
.shoa..he..ak.e.a.. k . e x . a . q . b A e t t D . . p s .
.a.&pil..a.f....d..Ahald.d
.cuted..a..cdahg..2AA....hetore.
........
-.Cattmp.Aag....acaa..t..up.
neutalise it
7.2 Salts, alkalis and equations
This challenge task relates to 7.1 What is a salt?, 7.2 Preparing a salt using metal and acid, 7.3 Metal carbonates and
acids and 7.4 Forming salts by neutralisation from the Coursebook.
In this challenge task, you will use your knowledge to name salts, a base and an alkali. You will
also correct some formulae and write word equations.
1
Name a salt formed from the following:
a
b
hydrochloric acidS.ca'Am..chlorde
citric acid Sadium..cihate.
zinc and nitric acidncoate.
d
2
copper and sulfuric acid
-.capp.eA.ale.
These formulae are incorrect.
HSO,
HCI,
HNO
teso4
Write them correctly.
lodium.oxicde.
Sodium..hyduxide.
5 Explain how alklis and bases are related,
Give an example of a base.
3
4
Give an example of an alkali.
QXide...A....
-onIKLiomtMetal..ox\ceA..NA...Q2.LLE
form
.Dn..
6
Write a wordequation for the reaction between sulfuric acid and the alkali that contains sodium.
Sol um
7
hydrox ide t Sufwic aud
sodium sufete t o t r
Write aword equation for the reaction to prepare the salt copper chloride from copper carbonate.
Cypor Carbonate t hydchlore
Qcid
(arbon
copper t water +dioxide
Chlonde
b
produced.
were
B,
no
bubbles
B
milky.
became
limewater,
through
passed
was
gas
this
When
produced.
were
it
of
A,
gas
bubbles
containing
limewater
becoming
milky
A
test three
of
tubes.
test
different
tests. tube.
some
of
to in
liquid each
did each one
and
reactions
differentsample a
Forming task
salt?,
given
some
to
identify
of
C
is
a
7.3
Metal
acid,
and
metal
using
salt a
an
carbonates
substances.
powder.
ground-up
form
the
C,
use from
7.2
the
each
the
informationPreparing
in Coursebook.
and
A, you
B wil
7.1
by
neutralisation
What
task,
A
substances,
different
In relates
this
salts
challenge
to
three
7.4
and
had
placed
acids
This 7.3
substances
Mystery
Jon
containing
observedthe
They They
a
Theyadded
challenge
and
tubethe In
Nor
In
tube
the
pop
In the tube containing C, bubbles of gas were produced. When the students collected this gas and tested it with a lighted splint, there was
asqueaky pop.
After the substances had finished reacting, the students heated the three solutions (after filtering if necessary). They evaporated them to
dryness to form three crystalline substances:
substance A produced zinc sulfate
substance B produced iron chloride
substance C produced magnesium chloride.
1
Which gas did substance Aproduce?...COLbon..dioxle
2 Which gas did substarnce C produce? ....
ydrogen.
3 What general name is given tothe crystalline substances produced in this way, after evaporation?
4 Suggest which liquid wasadded to tube A.
5 Suggest which liquid was added to tube B.
Appea..Chlonale.
6 Suggest which liquid was added to tube C.
.......
7 Suggest what substance A could h¡ve been.
dal...AraQnate.
8
Suggest what substance B could have been.
9
Suggest what substance C could have been.
10 Write a word equation for the reaction involving substance A.
ane canbonate t
Sulfumiccacid ’
zincsutfate + Carbon diordu + water
belowion
’
ion
chloide
t
teatea
copper.y
12 Write aword equation for the reaction involving substance C.
11 Write a word equation for the reaction involving substance B.
iron t Copper chloide
magneium + hydrochonc 0cid-magnesm ch londe t hyd ngen
Preparing commonsalts
Salts
1 Identify two uses of calcium
chloride. Tick () two boxes.
herbicides
setting concrete
bleaching paper
drying agents
2 Identify two uses of zinc sulfate. Tick (/)
making coSmetics
two boxes.
sewage treatment
food processing
Acids and their salts
3 Name the salt produced by each acid.
hydrochloric acid..Chlonde
Sulfate
sulfuric acid..
nitric acid..
nitnate
4 Write the word equations for the following reactions:
a magnesium and nitric acid MMaAnesium.t.nibis..aamgneium nihau t
t
b lead and hydrochloric acid Lead + hydnchlonc acd ’ lead chlonda
hyadrgcn
hadnagn
c aluminium and sulfuric acid .aumánium.t Sultunc a ud
46
lumindm sultate +
ydgen
10Preparing common salts
5 a
Howdothefibres in afilter paper help in the process of filtration?
rom
meh, ike a sieve he liquid can pass
Hysoughte
mal..halea. lyetiwen thu hbnu but
Hht
bru prevent the solide from peming
paaing Tuat
thiough
filtrate?
b What is the
c What is the
residue?
6 Describe what happens in the process known as evaporation.
Alhe.
ate.has..NapenCted.
7a What is a crystal?
Aclid.autink.t..a..ide.
b How would you make crystals of a substance?
SSolve dheAbatance....to...mak...a.
cencentated Altien.Placa..aA.. Naporating.casl..
-ppy.A..heat..sQAICA..A20M M....u.Cbut not boi)
thn leave to cool and let all the
behnd
tale
crys
leare
to
water evaporate
.
47
CHEMISTRY
Preparing a salt from a metal and
8 a Label the diagram for the
anc
an acid
preparation of zinc chloride below.
nleson a spoon or spatula
conicoal
hydrochloric auid i the
fask
4ns..grandes ià hydch one aed
they are in the wrona
b These are the stages involved in the preparation of zinc chloride, but
they occur.
order. Arrange them correctly by numbering them in the order in which
3
ina filter funnel.
A The flask contents are poured through a filter paper
B The reactants are mixed together in a conical flask.
C Metal remains on the filter paper and liquid passes through into a beaker.
D Bubbles are formed and pass through the acid.
c By what process is the final product obtained?
Evaparatien.
Preparing asalt from a metalcarbonate and an acid
9 a These are the stages in the preparation of a salt from a metal carbonate, but they are in the
wrong order. Arrange them correctly by numbering them inthe order inwhich they occur.
3
A Look for the end of bubbling in the mixture.
B Add the solid to the acid.
C Leave the heated solidto cool.
D Heat the liquid in a heat-proof container until a solid appears.
6
E Pour the acid into a container.
FTransfer the separated liquid to a heat-proof
G Separate the solid from the liquid.
48
container.
5
10 Preparing common salts
What processissperformed at the end toremove any remaining liquid?
The.solid.de.)
-patted.awith.a.papea..towel..to.rcmor...any
nemaining water on the cystals:from copper carbonate and
preparation of copper
Writethe equation for the
40a hydrochloricacid.
chloride
Coppea.Anbenale.AAe.hydoch loris.. uid
.SePer.chloride t .Carbon..dioxide. woter
b Why do you need to add
excess copper carbonate?
To.make....Swe.. .tha..ad..has.Meated
c Describe one safety precaution you would need
11 Hans is preparing copper sulfate using sulfuric
sample of copper carbonate.
with it
to take if you carried out this reaction.
acid. He has a sample of copper metal and a
a Which sample should he use?
He cam.us...eatae.Sample.
b Explain your answer.
Sultate
49
5Reactivity
> 5.3 Salts
Exercise 5.3A Which acid is used to make which saa
Focus
In this exercise, you willidentify which acid is used to produce a salt.
Then you identify a salt from its formula.
1
Link the name of the acid with its formula, and with the name
of the salt it produces.
Draw lines to link the boxes. Use a ruler.
2
Acid
Formula
Salt
hydrochloric acid
HNO,
sulfates
sulfuric acid
HCI
nitrates
nitric acid
H,SO4
chlorides
The following compounds are all salts of
magnesium. For each one,
state the acid that has been used to make the
salt.
magnesium chloride
magnesium sulfate
tydrochloie aid.
Sufunis aud
magnesium nitrate..mitric ad
3
Write the name of the salt next to its
formula.
NaCl...Sodium..chlonde.
CuS0,..apPeA...Sulfate.
CuCl,..opper..chlande.
KNO,..Potassium..nitrate.
4
Citric acid is found in fruit. What are salts of this acid
..Citrates
94
called?
5.3 Salts
Exercise 5.3B Making salts
Practice
salts are
you will explain how some
exercise,
Inthis
some
wordequations.
made and practise
could makethe salt zinc nitrate using zinc metal.
Explainhowyou
nitic aud
inocilute
some...KinG..metal.
Place
1
put yeur itt
pten it has. atoppecd..Heacting.
and heat
an..evporang..asin.
into..
uten.
cryala
prduu
maiamd
h..
to.ewaperut.
ntly
xinc nate
2
Write the word equation for this
reaction.
inGt.niie..aa..n...nitate.t hydrogen
sulfate
3 Explain why you could not make silver
by that method.
KLvenu..mauch.des...Heactine.than xinc amd
.Mill..net..Meaut..ith..dlue..uic acid
4 Explain why you could not make potassium sulfate by that
method.
fotaaiun..a..an..e... uactie.thane wold
be.an..explogine,..eaution.tpotassium
aid
wene pldced
metal
n diute sutfwlc
sulfuricacid
J Copper sulfate is made by mixing copper oxide with
and gently heating it.
Why is it important that the acid mixture does not boil?
b
fum theaid
ginn.
bnl.be
Write the word equation for the reaction.
Coppe.axide t..sulfunic audcOPpes sutfali + water
95>
5Reactivity
6
Write the word equations for the following reactions:
magnesium and nitric acid
magneuium..mtia.
b
aud
copper oxide and nitric acid
magnciun.t..ydrogen.
nitrate
ic
CApper.axide...t.nuhet.GORPea...t.water..
ad
zinc and hydrochloric acid
d
nrate
acid
zinc and sulfuric acid
zin.t.sukuni..nhydayn.
Sulfate
aud
Exercise 5.3C Practical steps for making salts
Challenge
Inthis exercise, you willdescribe in detail the practical steps needed to
produce a salt using an oxide and an acid.
1
Why is copper chloride not made by reacting copper with dilute
sulfuric acid?
Copper.chlend.cannat.be.made.oy. neazlin.sgper with dilute
Suue arecl.becauueto.make...a.chlande,..yQu..uwQuld need to
2
Ue hydrochlonic aid and copper is unteactibe and does not
Describe the three steps involved in producing crystals of the salt nent it
copper chloride. For each step, describe the method and include the amy calut acd
safety precautions needed. Use diagrams if they help your answer.
aid...ExeAS.cappea. 0xide.iu. .added... syfunic aid
L¢.a..beakea..Thia. ia..heated.gnty..and. stimed
.Conutanty..hen..a calaua.chamge.Lto. blue) i Seen,
you. shauld..shyp.heatag...Sajerypncaukanin :: wea
boil the aud mixtwe, a
ginen off
96
hamul ume
Cve
5.4 Other ways of making salts
The. stwnd step ia do. futer thu moxtwne. The
he.kiltate. io.a. JAlditn.9.. ceppr...s ufote No
addioral. Salcly. prrcautens...necd to be taten
trom
(t
khun.small..cytala..em.....thu..usten
tarke..to...pka.
p.haatun...an.allew the
Salety prLAlanA..Aear..dafaty.gass and
take.caA.ae..hu.ht.luten..nay
.pit..md..au..you.
> 5.4 Other ways of
making salts
Exercise 5.4A Preparing copper chloride
Focus
In this exercise, you will explain the steps in the formation of a salt.
You willalso consider some of the safety precautions
needed.
Zara and Sofia are preparing the salt copper chloride. Zara pours some
hydrochloric acid into a beaker. Then Sofia adds some copper carbonate.
97>
5Reactivity
copper
carbonate
hydrochloric acid
1
hydrochloric acid
What happens when Sofia adds the copper carbonate to the acid?
he.copper.Carbonate...McaLt..wath..the auid ad
..carbon.aioxid.
gao.agitn.4f.
Sofia adds more and more copper carbonate until there is no more
reaction. There is some unreacted copper carbonate left in the
beaker. Sofia filters the mixture.
filtrate
2
3
What is left in the filter paper?
(unreatd.cppe. .Carborate
The filtrate passes through the filter paper into the flask.
What is this liquid?
A.
4
mixane.ef watex and
ulion.f.cappe.chloxideC
cOPper chlonde)
Next, Zara
and Sofia want to produce crystals of the sált.
What must they do?
Plheat.it.to..evapunate..f.th.
au.khe.l ake.ia. an.cuaponatwater...and
iy. leave
basin and
the cryfals
98
5.4 Other ways of making salts
5
Why must they be very careful when they
6
What should they do to reduce the
carry out this step?
whun th doluton.wdeing..heuladlt tenda to
4pit..and thio Can bwn
hazard?
They..shaud.. wear..sately glasa. to prerent
.0amagc..D.hus..ya.,.dake..spal..ane when
Npenating..cdah..din..eff the heat when
.clou.D.u
the douton
beguns
7
Write the word equation for this reaction.
copper +
carbonate
hloic
Copper
+
+
chlonide
Carbon
dioxice
Exercise 5.4B Preparing potassium chloride
Practice
In this exercise, you will describe the steps needed in some practical
work toproduce a salt from an acid and an alkali.
Zara and Marcus want to prepare the salt potassium chloride,
using potassium hydroxide.
1
Which acid should they use?
yanchtenc...aud.
2
For the first step in this process, Zara and Marcus put 20 cm³
of potassium hydroxide in a conical flask. They use the acid to
neutralise it.
List the equipment they willneed for this first step in the process.
.M eaauing..aid.keakeu.C.conical..klat),
hyarelane...aud.bunette.. stand..
univeAal.ndicater..shitct..selutwn..
99
5 Reactivity
3
Deseribe the method for carrving out this step.
Include any safetyprecautions.
ta.00.
Put..on. sacly glaes. Fint..add adnp of
lunewal. indicator..saluleoh n. the. potaan
Aydvxide isthe beater, which tum blue.
.Set. 4p.the..burete...and.dl..wth. acid
Add..aud..alittle..
aa.tome....o.bhe.
petasai um..hydroxide...and. switl.the.
beaken..to..mix.the. content.
4
How will they know when the potassium hydroxide is neutralised?
khen.they.kar. See the.uninenalindi caler
..sauton.aunn.o...lue.t.
5
When the potassium hydroxide is neutralised, Zara and Marcus
have a coloured solution. How do they remove the colour, so that
the crystals of potassium chloride are pure?
Add.chaxcoal.to the.neutral.satin.
.t.Kmore...tha.calous.Ihen..the. soluten.
Shauld.be..ltered..t.remas...the. piescf charoal
6
Write the word equation for the neutralisation reaction.
potasoium
hydoida
7
hydrochlonc
’
aid
potasium + waler
Chloride
Write the symbol equation for this reaction.
KoH
100 >
+ Hcl
KcI
+ Ha0.
5.4 Other ways of making salts
Exercise 5.4C Mystery substances
Challenge
In thisexercise, you will use theinformation given to identify some
substances.
Arun and Marcus had three diflerent substances, A. B and C each
in the form of powder.
A
B
C
They placed a sample of cach in one of three different test tubes.
Thev added a different liquid to each test tube.
They observed the reactions and did some tests.
In the tube containing A, bubbles of gas
were produced. When this gas was passed
through limewater, it became milky.
limewater
becoming
milky
A
In thetube containing B, no bubbles were
produced.
B
101 >
5 Reactivity
pop
In the tube containing C, bubbles of
gas were produced. When the students
collected this gas and tested it with the
lighted splint, there was a squeaky pop.
C
After these substances had finished reacting, Arun and Marcus heated
the three solutions (after filtering where necessary). They evaporated the
substances to dryness to form three crystalline substances:
substanceA produced zinc sulfate
substance B produced iron chloride
substance Cproduced magnesium chloride.
Which gas did substance A produce?
1
carbon.doxide
2
Which gas did substance C produce?
3
hytrogen.
Which general
name is given to the crystalline substances produced
in this way, after evaporation?
Salts
4
Suggest which liquid was added to tube A.
Sufuric acid
5
Suggest which liquid was added to tube B.
chlonde
..a.selulan.f.cappea.chlomda.Camy.
veachviy Seni)
ametal below iron
102>
on the
5.5 Rearranging atoms
6
Suggest which liquid was added to tube C
7
Suggest what substance A could have
nyodvchlonc Qcid
been
Casbonate
Suggest what substance B could have been.
9
Suggest what substance C could have been.
10 Write a word equation for the reaction involving substance A.
....
11 Write a word equation for the reaction involving substance B.
nom.t..cOPPeo.chlonlde.iron.chloridt cOppe r
12 Write a word equation for the reaction involving substance C.
chonce
>5.5 Rearranging atoms
Exercise 5.5A What happens to the atoms
and the mass when chemicals react?
Focus
Inthis exercise, you will develop your understanding of how atoms
rearrange in a chemical reaction and look at what happens to the mass
of products in a reaction.
When chemicals react together, none of the atoms is lost.
Ihey rearrange to make other chemicals.
103>
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s.
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CAMBRIDGE LOWER SECONDARY CHECKPOINT
PRACTISE QUESTIONS -MARKSCHEMS
Subject: Chemistry- Stage - 9
ar
te
Topic: Preparing Common Salts Set-2
1
Dilute sulfuric acid is used to make salts known as sulfates.
m
A method consisting of three steps is used to make zinc sulfate from zinc carbonate.
Add an excess of zinc carbonate to 20 cm3 of 0.4 mol / dm3 dilute sulfuric acid until
the reaction is complete.
step 2
Filter the mixture.
step 3
Heat the filtrate until a saturated solution forms and then allow it to crystallise.
w
w
w
.s
step 1
(i)
Name a suitable piece of apparatus for measuring 20 cm3 of dilute sulfuric acid in step 1.
....................................................................................................................................... [1]
(ii)
State two observations which would show that the reaction is complete in step 1.
1 ..........................................................................................................................................
2 ..........................................................................................................................................
[2]
(iii)
Why is it important to add an excess of zinc carbonate in step 1?
....................................................................................................................................... [1]
(iv)
What is meant by the term saturated solution in step 3?
.............................................................................................................................................
....................................................................................................................................... [2]
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
Smart Exam Resources 1
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MARKING SCHEME:
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Chemistry
Smart Exam Resources 2
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Soluble salts can be made using a base and an acid.
m
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2
(a) Complete this method of preparing dry crystals of the soluble salt
cobalt(II) chloride-6-water from the insoluble base cobalt(II) carbonate.
te
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Step 1
Add an excess of cobalt(II) carbonate to hot dilute hydrochloric acid.
ar
Step 2
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.s
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...........................................................................................................................................
...........................................................................................................................................
w
w
Step 3
...........................................................................................................................................
...........................................................................................................................................
Step 4
...........................................................................................................................................
..................................................................................................................................... [4]
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
Smart Exam Resources 3
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MARK SCHEME:
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
Smart Exam Resources 4
s.
ce
ur
The diagrams show the stages in the preparation of zinc nitrate crystals from lumps of zinc
m
re
so
carbonate.
zinc carbonate
zinc carbonate
dilute
nitric acid
stage 1
stage 2
bubbles
of gas
stage 3
w
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3
zinc
nitrate
solution
unreacted
zinc
carbonate
stage 4
heat
stage 5
stage 6
(a) Complete the boxes to show the apparatus used.
[2]
(b) Use the diagrams to write a list of instructions for the stages of this preparation.
(i)
stages 1, 2, 3 and 4
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [3]
(ii)
stage 5
....................................................................................................................................... [1]
(iii)
stage 6
.............................................................................................................................................
....................................................................................................................................... [2]
[Total: 8]
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
Smart Exam Resources 5
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MARKING SCHEME
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Chemistry
Smart Exam Resources 6
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A student reacted excess iron powder with sulfuric acid to prepare a solution of iron(II)
sulfate.
The diagram shows the procedure followed in three stages.
2
iron powder was added
until all the sulfuric acid
had reacted
w
w
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.s
m
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50 cm3 of dilute sulfuric
acid was measured and
added to a beaker
heat
3
the mixture was
allowed to cool
solution of
iron(II) sulfate
(a) Complete the boxes to identify the pieces of apparatus labelled.
[2]
(b) How would the student know when all of the sulfuric acid had reacted? Give two reasons.
1 ........................................................................................................................................
2 .................................................................................................................................. [2]
(c) Describe the effect of boiling the solution of iron(II) sulfate for several minutes.
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [3]
[Total: 7]
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
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MARKING SCHEME
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Chemistry
Smart Exam Resources 8
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Smart Exam Resources
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CAMBRIDGE LOWER SECONDARY CHECKPOINT
PRACTISE QUESTIONS -MARKSCHEMS
Subject: Chemistry- Stage - 9
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Topic: Preparing Common Salts Set-1
18 °C
sodium hydroxide
solution at 18 °C
22 °C
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student adds an aqueous solution of sodium hydroxide to an aqueous solution of ethanoic acid.
1 AShe
measures the temperature before and after the addition of sodium hydroxide.
ethanoic acid
solution
The product of the reaction is a salt called sodium ethanoate.
Describe how you would prepare pure, dry crystals of sodium ethanoate from a solution of
sodium ethanoate in water.
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0620/23/M/J/15
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
Smart Exam Resources 1
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MARK SCHEME:
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Any three of:
• evaporation/ heat solution/leave the solution;
• to crystallisation point/to form crystals;
• filter off crystals / pick out crystals;
• dry crystals between filter papers / heat gently / heat to just above 100°C; 3
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
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Leave the mixture until no more bubbles are seen.
B
Leave the mixture at room temperature to form more crystals.
C
Add an excess of magnesium to dilute hydrochloric acid.
D
Warm the filtrate to the point of crystallisation.
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The following statements are about the procedure for making crystals of hydrated
magnesium chloride from magnesium and dilute hydrochloric acid.
Filter off the crystals and dry between filter papers.
F
Filter off the excess magnesium.
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Put the statements A, B, C, D, E and F in the correct order.
The first one has been done for you.
C
[2]
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
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(C), A, F, D, B, E (2)
if 2 marks not scored 1 mark for 1 consecutive pair reversed
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
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3 (a) Dilute hydrochloric acid reacts with zinc.
+
hydrochloric
acid
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+
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[2]
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zinc
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Complete the word equation for this reaction.
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(b) The following statements are about the procedure for making crystals of hydrated zinc sulfate
from zinc and dilute sulfuric acid.
A
Warm the mixture until no more bubbles are seen.
B
Add excess zinc to dilute sulfuric acid.
C
Warm the filtrate to the point of crystallisation.
D
Leave the mixture at room temperature to form more crystals.
E
Filter off the excess zinc.
F
Filter off the crystals and dry between filter papers.
Put the statements A, B, C, D, E and F in the correct order.
The first one has been done for you.
B
[2]
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
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MARK SCHEME:
(a) (hydrochloric acid + zinc) → zinc chloride (1) + hydrogen (1) 2
(b)(B), A, E, C, D, F (2)
If 2 marks not scored: 1 mark for 1 consecutive pair reversed
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
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+
magnesium
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+
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sulfuric acid
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Complete the word equation for the reaction of dilute sulfuric acid with magnesium.
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[2]
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
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magnesium sulfate (1)
hydrogen (1)
Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
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Magnesium sulfate and lead(II) sulfate are examples of salts.
(a) A student prepared magnesium sulfate crystals starting from magnesium carbonate. The
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student carried out the experiment in four steps.
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step 1
The student added excess magnesium carbonate to a small volume of
dilute sulfuric acid until no more magnesium carbonate would react.
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step 2 The student filtered the mixture.
(i)
step 3 The student heated the filtrate obtained from step 2 until it was saturated.
step 4 T
he student allowed the hot filtrate to cool to room temperature and then removed
the crystals which formed.
How did the student know when the reaction had finished in step 1?
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(ii)
Name
the residue in step 2.
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(iii)
A saturated solution forms in step 3.
What is a saturated solution?
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(iv)
Explain why magnesium sulfate crystals form during step 4.
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Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
Smart Exam Resources 9
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MARK SCHEME:
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Chemistry
Smart Exam Resources 10
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Describe how you would prepare a pure dry sample of copper(II) nitrate crystals in the
laboratory using dilute nitric acid and solid copper(II) carbonate.
Include a series of key steps in your answer.
You should include a chemical equation for the reaction.
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Cambridge Lower Secondary Checkpoints Stage 9 Practice Questions Chemistry
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MARK SCHEME:
Note:
• At the checkpoint stage, you may include a word equation
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Chemistry
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