13. ACIDS, BASES AND SALTS - Key
2. What is the PH scale? What does it measure?
acidity / basicity
3. a) Put the strips of papers with food items along the scale, according to their PH
factor, from high alkaline, to alkaline, low alkaline, low acid, acid to high acid.
HIGH
ALKALINE
LOW
LOW
ACID
HIGH
ALKALINE
ALKALINE
ACID
ACID
vegetable
Carrots, lettuce,
Goat milk,
Bananas,
Canned
Beef, pork,
juices,
zucchini,
soy milk,
plums,
fruit,
canned
parsley, raw
dates,blackcurrent, lentils, wild
processed
white rice, tuna,
spinach,
grapes, kiwi,
rice,
fruit juices, white
canned
broccoli,
apples, pears
buckwheat,
liver,
bread,
sardines,
celery, garlic,
strawberries,
oyster,
pastries,
parmasan,
herbal teas,
lemons,
whole
pasta,
black tea,
lemon water,
avocadoes,
milk,
fish,
coffee, beer,
dried figs,
tomatoes,
butter,
lamb,
liquor
raisins
oranges
yoghurt,
poultry,
white
eggs,
sugar
ketchup,
mustard
b) What problems might consuming too many acidic foods cause?
obesity, allergies, fatigue
4. Acids, bases and salts – definitions.
Watch the video1and complete the text below with missing pieces of information.
The Swedish chemist Svante Arrhenius introduced the theory of ionization and used this
theory to explain much about the behaviour of acids and bases.
An Arrhenius acid is defined as any compound that dissociates in aqueous solution to form
hydrogen ions.
HNO3(aq) → H+(aq) + NO3-(aq)
An Arrhenius base is defined as any compound that dissociates in aqueous solution to form
hydroxide ions.
KOH(aq) → K+(aq) + OH - (aq)
Salts are compounds that dissociate in aqueous solution releasing neither H+ nor OH ions.
KCl → K+ (aq) + Cl – (aq)
1
5. Classifying compounds
Using the Arrhenius definition, classify the following examples as acids, bases and salts
HBr – A (hydrogen bromide)
Mg(OH)2 – B (magnesium hydroxide)
HCl – A (hydrochloric acid)
KNO2 - A (potassium nitrite)
HFO4 - S (perfluoric acid)
Ba(OH)2 B (barium hydroxide)
KCl – S (potassium chloride)
H3 PO4 – A (phosphoric acid)
HClO – A (hypochlorous acid)
Al(OH)3 – B (aluminium hydroxide)
KC2 H 3O2 – S (potassium acetate)
NaCl – S (sodium chloride)
6. Naming acids and bases
a) Watch the video1 and complete the text below
Since bases are simply ionic compounds, they are named in the usual way:
NH4 OH – ammonium hydroxide
Al(OH)3 – aluminium hydroxide
Binary acids consist of 2 elements, the first being hydrogen. Binary acids are named using
the format: hydro+(root word of second element)+IC acid
Ternary acids consist of 3 elements. Do not use a prefix. Simply change the ending of the
polyatomic ion’s name and add the word acid. –ate ending becomes -ic and –ite becomes ous.
b) Now name the following acids:
HBr hydrobromic acid
HNO3 - nitric acid
HNO2 – nitrous acid
HI
– hydroiodic acid
(viz VIDEO)
H3 PO3 phosporous acid
HC2 H3 O2 acetic acid
H2 CO3 carbonic acid
HClO2 chlorous acid
HF hydrofluoric acid
H2 SO3 sulfurous acid
7. Naming salts;
a) Read the text below, and according to the information given, name the salts
underneath, as in the example.
The name of a salt has two parts. The first part comes from the metal in the base or carbonate,
or the metal itself if a reactive metal like magnesium or zinc is used. The second part of the
name comes from the acid used to make it. The names of salts made from hydrochloric acids
end in –chloride, while the name of salts made from sulfuric acid end in –sulfate.
metal
acid
1. sodium hydroxide reacts with hydrochloric acid
2. copper oxide
hydrochloric acid
3. sodium hydroxide
sulfuric acid
4. zinc oxide
sulfuric acid
5. ammonia
hydrochloric acid
2
to make
salt
sodium chloride
copper chloride
sodium sulfate
zinc sulfate
amonium chloride
b) Write formulas of the reactions above
1. NaOH + HCl → NaCl + H2O
2. Cu2O + 2 HCl → 2 CuCl + H2O
3. 2 NaOH + H2 SO4 → Na2SO4 + 2 H2O
4. 2 ZnO + H2 SO4 → Zn2SO4 + 2 H2O
5. NH3 + HCl → NH4Cl
8. Give formulas of these acids, bases and salts
boron silicide
sodium hydroxide
iron(III)chloride
sulfuric acid
B2Si
NaOH
FeCl3
H2SO4
magnesium phosphide Mg3P2
zinc hydroxide Zn (OH)2
aluminium sulfide Al2S3
sulfurous acid H2SO3
9. Chemistry quiz2
1. A solution has a pH of 4 - what does this mean?
It is acidic.
It is neutral.
It is alkaline.
2. Which of the statements below is correct?
Bases are acids that dissolve in water.
Bases are alkalis that dissolve in water.
Alkalis are bases that dissolve in water.
3. A liquid has a pH of 7. What does this tell you about the liquid?
It is water.
It is sodium chloride solution.
It is neutral.
4. Which salt is made when calcium carbonate reacts with hydrochloric acid?
sodium chloride
calcium chloride
calcium sulphate
5. Which pair of substances will react together to make copper sulfate?
copper and sulfuric acid
copper oxide and sulfuric acid
copper oxide and hydrochloric acid
6. Which is the correct order of methods for making a salt from an acid and an insoluble base?
filtration ==> evaporation ==> neutralisation
neutralisation ==> evaporation ==> filtration
neutralisation ==> filtration ==> evaporation
3
4