Chemistry 3 Revision Cards
Name________________________
Important information on Acids / Bases
Definitions:
Distinguish between Strong and Weak.
Acid (H+ Ions Present) – Proton Donor
Base (OH- Ions Present) – Proton Acceptor
Either:
Universal Indicator:
Strong acid red and weak acid yellow.
Neutral – Same number of H+ and OH- Ions.
Strong alkali purple and weak alkali blue.
Strong – Complete Ionisation
Conductivity test – Strong will conduct
better than the weak. More Ions!
Weak – Partial Ionisation
Titration – (4 marks)
Arrhenius, Bronsted and Lowry
Use the word Burette.
Add amount slowly.
Wait until indicator changes
Record amount.
Wash equipment
Repeat for reliability.
Arrhenius was first (student)– molecules
ionise in water.
B&L more experienced recognised
scientists.
Indicators!!
• Phenolphthalein:
Strong Alkali – Weak Acid titrations.
• Methyl Orange:
Strong Acid – Weak Alkali titrations.
• Any acid / base indicator:
Strong acid – Strong Alkali titrations
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Common question:
Dry hydrogen chloride is not acidic – why?
Hydrogen and chlorine are bonded.
No Hydrogen Ions present.
Titration Calculations
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1. NaOH(aq) + HCl (aq) NaCl(aq) + H2O(l)
15cm3 of HCl of 2.5M was used to neutralise 10cm3 of NaOH. What is the
concentration of NaOH?
HCl
NaOH
15 x 2.5 = 37.5
37.5 / 10 = 3.75m
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2. H2SO4 (aq) + 2NH3 (aq) → (NH4)2SO4 (aq)
The student found that 25.0 cm3 of ammonia solution reacted completely with 32.0
cm3 of sulfuric acid of concentration 0.050 moles per cubic decimetre.
H2SO4
2NH3
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32x0.05 = 1.6
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If you were asked to work out the molarity of H2SO4 instead of x 2 you would have to
divide by 2. Check your work booklet for examples.
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1.6 / 25 = 0.064 x 2 = 0.128m
Metal Ions – Flame Test
• Remember all Metal Ions are positively charged (+)
• Flame tests – Using a splint or metal loop dipped in an ionic
solution through a flame, will identify which ions are present
by the colour of the flame.
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Lithium (Li+) – Red Flame
Sodium (Na+) – Orange Flame
Potassium (K+) – Lilac Flame
Calcium (Ca2+) – Brick Red
Barium (Ba2+) - Green
Metal Ions - Sodium Hydroxide Test
• Other metal Ions can be identified by using Sodium Hydroxide.
• This method of analysis will normally produce a precipitate (ppt).
• Calcium (Ca2+) – White Ppt
• Magnesium (Mg2+) – White Ppt
• Aluminium (Al3+) - White Ppt – this will dissolve when excess sodium
hydroxide is added.
• Iron (Fe2+) – Green Ppt
• Iron (Fe3+) – Brown Ppt
• Copper (Cu2+) – Blue Ppt
• Ammonium (NH4+) This is a non-metal
• Add sodium hydroxide – No Ppt will be formed.
• When the solution is heated, use damp red litmus paper – this will turn
blue and a strong smell of ammonia will be present.
Non Metal Ions (-)
• Carbonates (CO32-)
• Add an acid to the solution, if carbonates are present CO2 will be
released. This will turn Limewater Cloudy.
• Carbonates will change colour when heated. Copper Carbonate
will change black as it turns into copper oxide.
• Zinc Carbonate will change from white to yellow as it changes
into zinc oxide.
• Sulphate Ions (SO42-)
• Using Barium Chloride will produce a white Ppt if sulphate
ions are present.
Non Metal Summary
• Carbonates CO32- – Add Acid – CO2 – Limewater Milky
• Sulphate SO42-– Barium Chloride - White Ppt
• Nitrates - NO3- – Add Aluminium Powder and sodium
hydroxide, gas produced – damp red litmus will turn blue.
• Halides – Group 7 – Add Silver Nitrate.
– Chlorides – White ppt
– Bromide – Cream ppt
– Iodide – Yellow ppt
Organic Chemicals
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Saturated and Unsaturated Hydrocarbons
Identified using Bromine Water
Saturated – Bromine water will stay orange / brown.
Unsaturated will de-colourise.
• Instrumental Analysis
• Quick, Accurate, sensitive and can detect very small amounts.
• Expensive and need special training to use them.
• The chemical analysis we have just looked at can not detect very
small amounts.
• There are lots of different methods of instrumental analysis – if in
doubt use Mass Spectrometer. This is used to test for elements and
+ ions.
Instrumental Analysis
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Atomic Spectrometers- Analyse energy (usually light) using a line emission
spectrum. Patterns are then matched to existing frequencies on a database.
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Infrared Spectroscopy- detects specific bonds in organic chemicals.
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Ultraviolet Spectroscopy- analyses levels of nitrates + phosphates in water.
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Nuclear magnetic resonance spectroscopy- used to detect some organic
molecules.
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Gas-liquid chromatography- separates gases through a column- identified by
the distance moved.
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Mass spectrometer- used for elements + ions. Masses of fragments used to
identify what is in a sample.
Empirical Formula of an Organic
Hydrocarbon
• 0.42g of a hydrocarbon burns in oxygen to
form 1.32g of CO2 and 0.54g of H2O
• Mr of CO2 is 44g. Mr of H2O is 18g.
• 1.32 / 44 = 0.03
• Formula = CH2
0.54 / 18 = 0.03
Development of the periodic table –
Newland and Mendeleev
• Newlands, and then Mendeleev, attempted to classify the elements
by arranging them in order of their atomic weights.
• PROBLEM WITH NEWLANDS
• Newland attempted to arrange the elements with his law of
octaves. (repeating pattern of similar properties every eighth
element) e.g. 7 elements between fluorine and chlorine and 7
between sodium and potassium on his table.
• His work was ignored because it had inconsistencies, he did not
leave gaps for undiscovered elements, some boxes had 2 elements
in and metals and non metals were mixed up.
Mendeleev
• Classified elements in terms of atomic weight.
• He left gaps for undiscovered elements
• He did reverse some elements to allow them to be in groups with similar
properties.
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Problems with Mendeleev
His work was not accepted at first because:
Some boxes had two elements in them
Copper and Silver were in group 1 and were unreactive unlike the others
There are metals and non metals in the same group
He left spaces / Gaps
Some chemists thought there were no more elements to discover
Modern Periodic Table
• Elements in the same group have similar properties – same
number of electrons in the outer shell.
• Reactivity?
Different Groups
Group 1 – Alkali Metals
– Add to water with Universal indicator in it you will see:
– Fizzing, flame, UI will turn purple (alkali) hence the name
Transition Metals
- Have coloured compounds, good conductors of heat and elec,
And coloured compounds.
Similar to each other because:
1. (transition elements usually) have same / similar number of outer / 4th shell
electrons
2. inner (3rd ) shell / energy level is being filled
No transition metals between Magnesium (Grp 2) and Aluminium (Grp 3) because they are
in period 2
which only have 2 levels and the 2nd level will only contain 8 electrons.
Compared to Alkali Metals
− Have higher melting points (except for mercury) and higher densities
− Are stronger and harder
− Are much less reactive and do not react as vigorously with water or oxygen.
Water
• Water is made safe to drink by removing solids and killing bacteria.
• Filtering and bubbling with chlorine.
• Tiny particles which are still suspended in the water are allowed to settle
out and fall to the bottom. This is called sedimentation.
• Chlorine is bubbled through the water to kill bacteria.
• Water filters containing carbon, silver and ion exchange resins can remove
some dissolved substances from tap water to improve the taste and
quality.
• Pure Water can be produced by DISTILLATION.
• However Drinking distilled water removes ions from the body which may
lead to health problems.
Hard Water
Soft Water
Contains Magnesium and Calcium Ions – Soft water readily forms lather with
soap.
from rock. Calcium is good for health.
Water that doesn't have enough calcium and
Hard water reacts with soap to form magnesium.
scum and so more soap is needed to
Soft water is treated water in which the only
form lather.
positively charged ion is sodium. Sodium is
bad for health – high blood pressure.
Scum is created when calcium ions form
an insoluble precipitate.
Soft water, on the other hand, may taste
salty and may not be suitable for
Using hard water can increase costs drinking.
because more soap is needed.
When hard water is heated it can
produce scale that reduces the efficiency
of heating systems and kettles.
Hard to Soft
• Making Hard Water Soft by removing dissolved
calcium and magnesium ions
• Adding sodium carbonate which reacts with the
calcium and magnesium ions forming a precipitate of
calcium carbonate and magnesium carbonate. This can
then be filtered.
• Using an ion exchange column containing hydrogen
ions or sodium ions which replace the calcium and
magnesium ions when hard water passes through the
column.
Solubility of Solids
• Solute – Solid being dissolved,
• Solvent – Liquid
• Solution – Dissolved Solute in Solvent
• Solubility of a solute increases as the
temperature of the solvent increases. Once no
more solute will dissolve the solution is said to
be SATURATED.
Solubility of Gases
• Many gases are soluble in water. Their solubility increases as the
temperature decreases and as the pressure increases.
• Gases as a solute dissolve and remain dissolved better under colder
temperatures. Think - as the temperature decreases, so does the kinetic
energy of any particle and just the opposite.
• Consider a can of coke. If it gets hot - the pressure inside increases, as it
does if you shake it. If you then open it, there is a sudden rush of carbon
dioxide coming out of solution and soda shoots everywhere. If you open
an almost frozen soda can, there is little release of gas from solution.
• Dissolved oxygen is essential for aquatic life. If the temperature of the
water increases, the amount of oxygen that is dissolved decreases.
Chemical Reactions
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BONDS BREAK (need energy) requires the Activation Energy (catalysts reduce this)
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BONDS FORM (releases energy)
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EXO – More energy is released from the forming of new bonds than was required
to break existing ones.
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ENDO – More energy is required to break existing bonds than is released when
new bonds form.
Calculating bond energies
If the bond energies of the reactants are greater than the products – the reaction is
endothermic
If the bond energies of the reactants are lower than the products – the reaction is
exothermic.
Endothermic and Exothermic Reaction
Graphs
Exothermic
A = Activation Energy – amount of energy
required to break existing bonds
B = Total amount of energy released from the
production of new bonds.
C= Amount of energy given out into the
surroundings
Endothermic
A = Activation Energy – amount of energy
required to break existing bonds
B = Total amount of energy released from the
production of new bonds.
C= Amount of energy absorbed from the
surroundings