Year 12 Chemistry Chemical Monitoring and Management Quiz 1 Solution
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1. Why are industrial combustion reactions monitored? Multiple Choice: 1 mark each
a) To maximise incomplete combustion.
b) To minimise incomplete combustion.
c) To oxidise the fuel.
d) To determine which type of fuel is the most suitable.
2. Identify four industrial uses of ammonia.
● make fertilisers ● make explosives ● make nitric acid
● refrigerant
4 marks
● make cleaning products
3. Write a balanced equation for the Haber process and identify two ways the rate of reaction can be
increased.
4 marks
N2 + 3H2 ⇌ 2NH3 The rate of reaction can be increased by using a catalyst and by increasing the
temperature. (Don’t confuse increasing the yield with increasing the rate of reaction!)
4. Why are the gases leaving the reactor in the Haber process cooled?
3 marks
The gases are cooled to condense the ammonia so it can be removed. According to Le Châtelier's principle,
removing the product for a reversible reaction will shift the equilibrium to the right, i.e. increase the yield
of ammonia. It is also done to reuse the unreacted nitrogen and hydrogen.
5. Explain the effect of adding a catalyst on the reaction temperature required for the Haber process. 2 marks
A catalyst lowers the required reaction temperature because it lowers the activation energy of the
reactants.
6. Identify and explain the compromise that must be made when determining the reaction conditions for the
industrial synthesis of ammonia via the Haber process.
3 marks
A temperature of around 500°C is used. A high yield is favoured by low temperature but high rate of
reaction is favoured by high temperature. Both yield and rate of reaction are important, so a compromise
must be made on the temperature.
7. Why does the yield of ammonia decrease with temperature in the Haber process?
a) The forward reaction absorbs heat
b) The ammonia produced in the reaction is increasingly decomposed as the temperature increases
c) Ammonia is unstable because it lacks hydrogen bonding
d) The forward reaction is endothermic
8. Define Le Châtelier's principle.
2 marks
When a system at equilibrium is subjected to change in concentration, temperature, volume, or pressure,
then the system readjusts itself to (partially) counteract the effect of the applied change and a new
equilibrium is established.
9. Identify the factors which can affect the equilibrium in a reversible reaction.
2 marks
•change in concentration •change in temperature •change in volume •change in gas pressure
10. Analyse the impact of increasing the pressure in the reaction vessel during the synthesis of ammonia via the
Haber process.
4 marks
N2 + 3H2 ⇌ 2NH3 There are 4 molecules of gas on the left and 2 molecules of gas on the right of the
equation so, according to Le Châtelier's principle, increasing the pressure will shift the reaction to the right
and therefore increase the yield of ammonia. Also, the reaction involves collisions between gas particles,
so a higher pressure will mean more frequent collisions and therefore a higher rate of reaction.
11. Why must the raw materials for the Haber process be monitored?
2 marks
Impurities in the feed can be adsorbed on to the surface of the catalyst and reduce the surface area of the
catalyst available for the reaction. Oxygen present can react explosively with the hydrogen to form water.
The water formed will condense out with the ammonia and contaminate the product.
12. Which test could be performed to test for the presence of barium ions?
a) Add a soluble sulfate salt
b) Add an insoluble sulfate salt
c) Dissolve by adding hydrochloric acid
d) Heat at high temperature until white barium oxide solid is observed
13. Which ion could be qualitatively tested using the flame test?
a) 𝑁𝑂3−
b) 𝑪𝒖𝟐+
c) 𝑆𝑂42−
d) 𝐶𝑙 −
14. A 1.000g sample of lawn fertiliser was analysed for sulfate content. The fertiliser was ground into a fine
powder then dissolved in water and filtered. The sulfate ions in the filtrate were precipitated by adding 50ml
of 0.1M BaCl2 solution then filtered using new filter paper. The clean filter paper had a mass of 2.007g and
the dried filter paper and precipitate had a mass of 2.077g. Calculate the percentage composition of sulfate
in the fertiliser.
2 marks
𝑴𝑺𝑶𝟒
𝒎𝒔𝒖𝒍𝒇𝒂𝒕𝒆
𝑴𝑩𝒂𝑺𝑶𝟒 × 𝒎𝑩𝒂𝑺𝑶𝟒
𝟎. 𝟒𝟏𝟏𝟔 × 𝟎. 𝟎𝟕𝟎
%𝒔𝒖𝒍𝒇𝒂𝒕𝒆 =
× 𝟏𝟎𝟎% =
× 𝟏𝟎𝟎% =
× 𝟏𝟎𝟎% = 𝟐. 𝟗%
𝒎𝒇𝒆𝒓𝒕𝒊𝒍𝒊𝒔𝒆𝒓
𝒎𝒇𝒆𝒓𝒕𝒊𝒍𝒊𝒔𝒆𝒓
𝟏. 𝟎𝟎𝟎
15. Identify one way the validity of the above procedure could be improved?
1 mark
●Dissolve the fertiliser in hydrochloric acid rather than water. ●Use excess BaCl 2 solution. ●Mix the bag
of fertiliser thoroughly before taking the sample to get a more representative sample.
16. How could the reliability of the above procedure be improved?
●Repeat the procedure multiple times.
1 mark
17. Why is it necessary to monitor the levels of phosphate ions in waterways?
a) Phosphate ions are extremely toxic to fish so even a small amount of phosphate will kill fish.
b) Phosphorus is a plant nutrient that can result in excessive plant growth and therefore high BOD.
c) Phosphorus glows at night and can attract parasitic insects that harm aquatic organisms.
d) Phosphorus is a radioactive element that emits gamma rays that can cause genetic mutations in fish.
18. Identify two sources of lead pollution.
2 marks
●Lead acid battery factory ●Renovating old houses painted with lead paint ●Lead smelters ●Lead solder
used to join water pipes
19. A manufacturer of multivitamins claims that its tablets contain the RDI of zinc for adult males (14mg). A
tablet was selected at random from a bottle and analysed for zinc content. The tablet was ground into a
powder then 400ml of 1M hydrochloric acid was added to the powder to dissolve the zinc. The solution was
divided into five 80ml aquilots and analysed using AAS. The average absorbance was found to be 0.195. Use
the average absorbance and the AAS calibration curve below to evaluate the manufacturer’s claim. 4 marks
concentration (ppm)
absorbance
0
0.003
20
0.097
40
0.204
60
0.306
80
0.428
100
0.515
From the calibration curve, the concentration corresponding to the average absorbance was 37.8ppm.
𝑹𝒆𝒄𝒂𝒍𝒍 𝒕𝒉𝒂𝒕 𝟏𝒑𝒑𝒎 = 𝟏𝒎𝒈
𝒎 = 𝟓 × 𝒄 × 𝒗 = 𝟓 × 𝟑𝟕. 𝟖𝒎𝒈
× 𝟎. 𝟎𝟖𝑳 = 𝟏𝟓. 𝟏𝟐𝒎𝒈
𝑳
𝑳
The tablet tested contained 15.12mg of zinc which exceeded the RDI, so the manufacturers claim was supported.
20. What are the layers of the atmosphere in order from ground level?
a) Atmosphere, hydrosphere, ozone layer, ionosphere
b) Troposphere, stratosphere, mesosphere, thermosphere
c) Biosphere, ozone layer, stratosphere, thermosphere
d) Stratosphere, ozone layer, mesosphere, ionosphere
21. Write balanced chemical equations for the production and decomposition of ozone by UV light and the
destruction of ozone by chlorine free radicals.
6 marks
𝑼𝑽
Production by UV: 𝑶𝟐 (𝒈) → 𝟐𝑶 ⋅(𝒈) then
𝑶𝟐 (𝒈) + 𝑶 ⋅(𝒈) ⟶ 𝑶𝟑 (𝒈)
𝑼𝑽
Decomposition by UV: 𝑶𝟑 (𝒈) → 𝑶𝟐 (𝒈) + 𝑶 ⋅(𝒈) then
Destruction by ·Cl: ⋅ 𝑪𝒍(𝒈) + 𝑶𝟑 (𝒈) ⟶⋅ 𝑪𝒍𝑶(𝒈) + 𝑶𝟐 (𝒈)
𝑶 ⋅(𝒈) + 𝑶 ⋅(𝒈) ⟶ 𝑶𝟐 (𝒈)
then
⋅ 𝑪𝒍𝑶(𝒈) + 𝑶 ⋅(𝒈) ⟶ 𝑪𝒍 ⋅(𝒈) + 𝑶𝟐 (𝒈)
22. Identify five significant pollutants found in the lower atmosphere and give one source for each.
oxides of sulfur (SOX)
oxides of nitrogen (NOX)
volatile organic compounds (VOC)
carbon monoxide (CO)
particulates
carbon dioxide (greenhouse gas)
methane (greenhouse gas)
ozone
10 marks
Smelting of sulfide ores, burning fuels containing sulfur
N2 and O2 from air reacting inside high temp. vehicle engine
Solvents, unburnt hydrocarbon fuels
Incomplete combustion of fossil fuels
Soot from incomplete combustion, dust from earthworks
Combustion of fossil fuels, land clearing
Anaerobic decomposition, ruminant animals
NO2 reacts with O2 in the presence of UV light
23. Ozone helps sustain life on Earth yet is also considered a pollutant. Discuss.
2 marks
Exposure to UV light can cause cancer and cataracts. Ozone in the stratosphere absorbs much of the UV
light so UV levels at the surface are reduced. However, ozone can irritate the eyes and respiratory system
of people and also produce photochemical smog so is considered a pollutant at ground level.
24. Ozone has co-ordinate covalent bonding. A co-ordinate covalent bond is a bond where both electrons in the
bond are provided by the same atom. Draw a labelled Lewis Dot diagram of ozone to illustrate this. 2 marks
25. Account for the fact that ozone is more soluble in water than diatomic oxygen in terms of atomic structure.
2 marks
Diatomic oxygen is a symmetrical molecule so is non-polar. Ozone is a non-symmetrical molecule so is
polar. Water is a polar solvent. Ozone dissolves better in water than diatomic oxygen because it is a polar
molecule.
26. What does the word allotrope mean?
a) An old name for ozone.
b) An old name for isotope.
c) Atoms of an element arranged in a covalent network structure.
d) Different arrangements of atoms in an element.
27. Rank diatomic oxygen, ozone and oxygen free radicals in order of increasing reactivity.
Least reactive
Most reactive
1 mark
Diatomic oxygen, ozone, oxygen free radicals
28. Draw the molecule 2-bromo-4-fluorobutane and write its chemical formula.
2 marks
CH3CHBrCH2CH2F
29. Draw, name and write the chemical formula for the molecule formed when the bromo and fluoro
groups are swapped in the molecule 2-bromo-4-fluorobutane.
3 marks
1-bromo-3-fluorobutane
CH2Br CH2CHFCH3
30. What word is used to describe the two compounds described in questions 28 and 29?
a) isotopes.
b) CFCs.
c) isomers.
d) argons.
31. What word is used to describe the two compounds described in questions 28 and 29?
a) halons.
b) BFCs.
c) teflons.
d) polymers.
32. Identify one disadvantage of using CFCs.
They destroy the ozone layer.
1 mark
33. What has been done to reduce the negative effects of CFCs.
1 mark
●They have been banned. ●They have been replaced with alternatives that are non or less destructive to
the ozone layer.
34. Identify six key parameters that are commonly used to determine water quality.
● concentration of common ions
● pH
● total dissolved solids
● dissolved oxygen
● hardness
● biochemical oxygen demand
6 marks
● turbidity
35. Explain what causes temporary hardness?
3 marks
Temporary hardness is due to the presence of the soluble salts calcium hydrogencarbonate Ca(HCO 3)2 and
magnesium hydrogencarbonate Mg(HCO3)2. Both calcium hydrogencarbonate and magnesium
hydrogencarbonate decompose when heated to form the insoluble calcium carbonate CaCO3 and
magnesium carbonate MgCO3. This happens when water is boiled. It is called temporary hardness because
boiling the water causes the CaCO3 and MgCO3 to precipitate meaning that the water above is now soft
(largely free of calcium and magnesium ions).
36. Explain what causes permanent hardness?
3 marks
Permanent hardness is due to the presence of the soluble salts calcium sulfate CaSO4 and magnesium
sulfate MgSO4. Both calcium sulfate and magnesium sulfate remain soluble when heated. It is called
permanent hardness because boiling the water does not cause the CaSO4 and MgSO4 to precipitate
meaning that the water above remains hard (has a high concentration of calcium and magnesium ions).
37. Identify three factors that affect the concentrations of ions in solution in natural bodies of water. 3 marks
● the frequency of rainfall (floods and droughts)
● water temperature
● evaporation rates
● soil type
● pollution sources, such as industrial waste or animal waste or fertiliser runoff
● land use
38. Outline the steps used to purify and sanitise mass water supplies.
6 marks
● sedimentation (settling using gravity) combined with flocculation (adding chemicals to cause small
particles to clump together and settle)
● filtration (typically through sand filters)
● disinfection (using chlorine, chloramines or ozone)
39. Compare and contrast the use of chlorine, chloramines or ozone for sterilising mass water supplies. 4 marks
Oxidising power
Cost
Lifetime in pipe network
Chlorine
high
low
short
Chloramines
medium
medium
long
Ozone
very high
high
very short