 GLOBAL CAPE CHEMISTRY LESSONS  CUNUPIA  739-2656  GLOBAL CAPE CHEMISTRY LESSONS  CUNUPIA  739-2656  GLOBAL CAPE CHEMISTRY

LESSONS  CUNUPIA  739-2656  GLOBAL CAPE CHEMISTRY LESSONS  CUNUPIA  739-2656  GLOBAL CAPE CHEMISTRY LESSONS  CUNUPIA
Question 1
1(a) The rate of a reaction is the change in concentration of a reagent or product with time at a stated
temperature.

1(b)(i) CaCO3(s) + 2HCl(aq)  CaCl2(aq) + H2O(l) + CO2(g)

1(b)(ii) From the balanced equation for the reaction,1 mole of CaCO3 produces 1 mole of CO2.
Moles of CaCO3 used = (mass of CaCO3 used/molar mass of CaCO3).
Moles of CaCO3 used = (1/100) mol. i.e. 0.01 mol.
Therefore, moles of CO2 produced = 0.01 mol.
Volume of CO2 produced at RTP = molar volume of gas at RTP × number of moles of gas.
Volume of CO2 produced at RTP = (24 000 × 0.01)cm3 = 240 cm3.

1(c)(i)
Test Temperature (C) Time Taken (s) Reciprocal Time (s-1)
1(c)(ii)
1 18 51.5 0.019

2 23 31.5 0.032

3 28 19.0 0.053

4 32 13.0 0.077

5 37 8.5 0.118

6 43 5.0 0.200
 1(c)(iii)
Question 1

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Question 1
1(d)(i) Increasing temperature increases the rate of reaction. Reciprocal time, which is an indicator of
reaction rate increases as temperature increases.

1(d)(ii) As temperature increases, more reagent particles have energies greater than or equal to the
activation energy, and collisions between reagent particles occur more frequently due to increased
kinetic energy. Both of these factors lead to more successful collisions per unit time and therefore a
faster/increased rate of reaction.

1(e) 0.154 s-1.

1(f) When the gas is bubbled through Ca(OH)2(aq) i.e. lime water, a white precipitate is initially formed.

Question 2
2(a)(i) Isotopes are atoms of the same element which have the same atomic number (number of protons)
but different mass numbers (numbers of neutrons).

2(a)(ii) Number of protons in both 35Cl and 37Cl = 17.

Number of neutrons in 35Cl = (mass number – atomic number) = (35-17) = 18.
Number of neutrons in 37Cl = (mass number – atomic number) = (37-17) = 20.
35Cl and 37Cl have the same number of protons and different numbers of neutrons, making them

isotopes of chlorine.

2(b) Two uses of radioisotopes are radiotherapy i.e. treatment of cancer (cobalt-60) and as a power
source/supply in pacemakers (plutonium-238).

2(c)(i) Cl2(g) + 2I-(aq)  2Cl-(aq) + I2(aq).

2(c)(ii) The yellow-green colour of chlorine gas disappeared and the colourless solution became dark/dirty
brown, as the chlorine gas came into contact with the solution.

2(d)(i) S(s) + O2(g)  SO2(g).

2(d)(ii) Sulfur is used in the manufacture of sulfuric acid.

2(d)(iii) Mg(s) + S(s)  MgS(s).

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Question 3
3(a) Compound X belongs to the alkanes.
Compound Y belongs to the alkenes.

3(b) Compound X is used as a fuel for cooking i.e. cooking gas.

Compound Y is used as a monomer for making the plastic polypropene which is used in packaging.

3(c)

Structure of Compound X Structure of Compound Y

3(d)(i)

3(d)(ii) Reagents: a few drops of concentrated sulfuric acid followed by water.

Reaction conditions: heating to 170 C at a pressure of 1 atmosphere.

3(e) Ethyl ethanoate.

3(f) C2H5OH(l) + CH3COOH(l) ⇌ CH3COOC2H5(l) + H2O(l)

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Question 4
4(a) Electrolysis is defined as the chemical decomposition of an electrolyte by the passage of an electric
current.

4(b)(I) Effect: Bulb will not light.

Reason: There are no mobile, charged particles available to carry charge and conduct electricity since
the Na+ and Cl- ions are held in fixed positions in the lattice by strong electrostatic forces of
attraction.

4(b)(ii) Effect: Bulb will light brightly.

Reason: There is a large number of mobile H+(aq) and Cl-(aq) ions which are mobile and able to carry
charge, due to the complete dissociation of HCl in water.

4(b)(iii) Effect: Bulb will not light.

Reason: Ethanol does not dissociate to any degree which will allow the presence of enough mobile
ions to conduct an electric current.

4(b)(iv) Effect: Bulb will light brightly.

Reason: There is a large number of delocalized electrons which are able to move through the metallic
lattice structure under the influence of a potential difference, thereby conducting electricity.

4(c) Quantity of electricity passed = I × t = (6 × (3 × 60)) C = 1080 C.

One mole of Pb is produced by (2 × 96 500) i.e. 193 000 C.
Moles of lead produced in experiment = (1080/193000) mol. i.e. 0.0056 mol.
Mass of lead produced = (moles of lead produced × molar mass of lead).
Mass of lead produced = (0.0056 × 207) g = 1.16 g.
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Question 5
5(a) Fermentation is the conversion of carbohydrates to ethanol and carbon dioxide by enzymes present
in yeast. Raw materials are yeast and a carbohydrate source such as fruit juice. The equation for this
process is C6H12O6(aq)  2C2H5OH(aq) + 2CO2(g).

5(b) Soap is made by the alkaline hydrolysis of fats and oils. It is achieved by boiling the fat/oil with
sodium hydroxide. The resulting solution is treated with NaCl(aq) and solid soap is recovered by
filtration of the mixture. Soap is the sodium salt of the long chain fatty acid, and is produced
alongside glycerol in this process. The structure of the soap is shown below.

5(c)(i) Polymer BB: Type of polymer – polyamide. Type of polymerization – condensation polymerization.

Polymer CC: Type of polymer – polyalkene. Type of polymerization – addition polymerization.

5(c)(ii)
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Question 6
6(a)(i) Magnesium is required to make green chlorophyll. If there is insufficient magnesium available, less
chlorophyll will be formed and leaves will appear yellow. Chlorophyll is used in the process of
photosynthesis which yields carbohydrates. Carbohydrates are stored in the tomatoes. Low
production of carbohydrates would lead to smaller tomatoes, and fewer tomatoes being produced
by the plant.

6(a)(ii) Potassium is also important to plant health and its deficiency results in yellowing of older leaves,
starting at the tips and eventually spreading to the entire leaf.

6(b) Metal: Lead.

Effect on health: Causes retardation in young children.
Effect on the environment: Contaminates water making it unusable by humans.

Non-metal: Sulfur.
Effect on health: Causes irritation of the respiratory tract.
Effect on the environment: Produces acid rain which results in the acidification of water bodies and
the death of animals which live there.

6(c) Green chemistry is the utilization of a set of principles that reduce or eliminate the use of, and
generation of hazardous substances in the design, manufacture and application of chemical products.
Greener fuels have been produced by eliminating the use of leaded compounds in fuels, and more
efficient removal of sulfur from fuels. These measures have reduced and/or eliminated the emission
of harmful lead and sulfur compounds into the environment.