CHEMISTRY 2022

Question 1

Suggest why poly(butene) insulation must be removed from scrap copper wire before
the copper is recycled

Answer 1

(otherwise) the copper
(produced) would be impure

Question 2

Explain why the mass of the test tube and contents decreased.

Answer 2

water vapour was produced
(so) water (vapour) escaped
(from the tube)

Question 3

Suggest why the test tube and contents were heated until the mass did not change

Answer 3

(so that) the reaction was
complete
allow (so that) no more water
(vapour) was produced

Question 4

Evaluate the use of glass for milk bottles compared with the use of a polymer for
milk bottles.
Use features of life cycle assessments (LCAs) in your answer.
Use Table 2

Answer 4

raw materials
* crude oil is finite
* quarrying / mining pollute the environment
* glass uses more energy to process raw materials
manufacturing
* glass uses more energy to make bottles
* glass is heavier so takes more energy to transport
use and operation
* glass bottles are reusable
* reuse of glass conserves (natural) resources
* reuse of glass consumes energy during washing
* reuse of glass consumes water during washing
disposal
* both glass and polymer bottles can be recycled
* recycling polymer conserves finite resources
* recycling glass and polymer uses less energy than making new
glass and polymer
* both methods reduce use of landfill
other points
* energy needed may be derived from fossil fuels
* use of fossil fuels causes (specified) pollution
* total energy for glass (bottle) (7500 kJ) is greater than total
energy for polymer (bottle) (1800 kJ)
reasoned judgement

Question 5

how many grams in 1cm^3

Answer 5

1 gram

Question 6

Petrol obtained from crude oil contains sulfur impurities.
Explain why sulfur impurities are removed before petrol is burned in car engine

Answer 6

(when burned sulfur impurities)
produce sulfur dioxide
(which) causes acid rain
or
(which) causes respiratory
problems

Question 7

Complete the equation for the complete combustion of C9H20
You should balance the equation.
C9H20 + __________ → __________ + __________

Answer 7

C9H20 + 14O2 → 9CO2 +10H2O
hydrocarbon + oxygen –> carbon dioxide + water

Question 8

A student predicted that heavy fuel oil is more viscous than kerosene.
The student’s prediction was correct.
Justify the student’s prediction

Answer 8

as molecular size increases
viscosity increases
(and) heavy fuel oil has larger
molecules (than kerosene

Question 9

Which two are useful materials produced from this feedstock?

Answer 9

detergents
solvents

Question 10

Suggest what the company means by ‘pure’.

Answer 10

(the water is) unadulterated
or
(the water is) in its natural state

Question 11

Natural gas is a fossil fuel.
Describe how deposits of natural gas were formed

Answer 11

plankton (died)
and (the organisms) were
covered by sediments
and subjected to
high temperature
and
high pressure
(over millions of years)

Question 12

Give the sources of the nitrogen and of the hydrogen used in the Haber process

Answer 12

(nitrogen) air
(hydrogen) natural gas

Question 13

How does the equation for the reaction show that the atom economy of the
forward reaction is 100%

Answer 13

there is only one product

Question 14

Explain how the ammonia produced is separated from the unreacted nitrogen and
hydrogen in X

Answer 14

(mixture is) cooled
(so that only) ammonia liquefies

Question 15

Explain why these conditions are chosen for economical production of ammonia in the
Haber process:
* a temperature of 450 °C
* a pressure of 200 atmospheres
* the presence of an iron catalyst.

Answer 15

rate
* higher temperature gives higher rate because of more frequent
collisions
* higher temperature gives higher rate because more particles
have the activation energy
* higher pressure gives higher rate because of more frequent
collisions
* use of catalyst gives higher rate because the activation energy is
lowered
equilibrium
* higher temperature shifts the position of equilibrium to the left
because reaction is exothermic
* higher pressure shifts the position of equilibrium to the right
because more molecules on left-hand side
* use of catalyst has no effect on the position of equilibrium
other factors
* higher temperature (than 450°C) uses more energy so increases
costs
* higher pressure (than 200 atmospheres) uses more energy so
increases costs
* higher pressure (than 200 atmospheres) requires stronger
reaction vessels so increases costs
* use of a catalyst reduces energy costs
compromise
* the temperature chosen is a compromise between rate of
reaction and position of equilibrium
* the temperature chosen is a compromise between rate and cost
* the pressure chosen is a compromise between yield / rate and
cos

Question 16

Sulfur is produced in the reaction.
Why does the mixture become cloudy?

Answer 16

(sulfur is a) precipitate / solid
or
(sulfur is an) insoluble
substance

Question 17

Explain why the rate of reaction changes between 0 and 60 seconds.
Answer in terms of concentration.
Use Figure 7

Answer 17

rate decreases
(because) concentration of
reactants decreases
alternative approach:
greatest rate at start (1)
(because) greatest
concentration of reactants at
start (1

Question 18

Sketch a line on Figure 8 to show the results you would predict for 0.20 mol/dm3
sodium thiosulfate solution

Answer 18

start at same co ordinate always

Question 19

What name is given to similar results obtained on different days under the same
conditions by the same student?

Answer 19

repeatable