Question
(a) This question is about elements.
aluminium
carbon
iron
hydrogen
oxygen
silicon
sodium
sulfur
Answer the following questions about these elements.
Each element may be used once, more than once or not at all.
(i) Name the element that can be used as a fuel………………………………………………………………………………………………………………………. [1]
(ii) Name the element that forms an oxide with a similar structure to diamond………………………………………………………………………………………………………………………. [1]
(iii) Name the element that forms an amphoteric oxide………………………………………………………………………………………………………………………. [1]
(iv) Name the element that has oxidation states of +2 and +3………………………………………………………………………………………………………………………. [1]
(v) Name the element extracted from bauxite………………………………………………………………………………………………………………………. [1]
(vi) Name the element that has atoms with the electronic structure 2,6………………………………………………………………………………………………………………………. [1]
(b) Iron rusts when it is in contact with oxygen and water.
(i) Explain how sacrificial protection prevents rusting………………………………………………………………………………………………………………………. [2]
(ii) State one other method of rust prevention………………………………………………………………………………………………………………………. [1] [Total: 9]
▶️Answer/Explanation
Ans:
1(a)(i) hydrogen / carbon 1
1(a)(ii) silicon 1
1(a)(iii) aluminium 1
1(a)(iv) iron 1
1(a)(v) aluminium 1
1(a)(vi) oxygen 1
1(b)(i) metal higher in reactivity series / metal more reactive (than iron) / allow named metal e.g. magnesium or zinc (1)
zinc corrodes/oxidises/reacts in preference to iron (1)
1(b)(ii) any barrier method e.g. painting
Question
Zinc is extracted from an ore containing zinc sulfide.
(a) State the name of this zinc ore…………………………………………………………………………………………………………………………….. [1]
(b) This ore is converted to zinc oxide, ZnO.
Zinc oxide is then reacted with carbon.
(i) Write a chemical equation for the reaction of zinc oxide with carbon………………………………………………………………………………………………………………………. [1]
(ii) State what type of chemical change happens to the zinc in zinc oxide in this reaction.
Explain your answer.
chemical change …………………………………………………………………………………………………..
explanation ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………….[2]
(iii) Explain why aluminium is not extracted from aluminium oxide by heating with carbon………………………………………………………………………………………………………………………. [1]
(iv) Suggest an alternative method for the extraction of zinc from zinc oxide……………………………………………………………………………………………………………………… [1]
(c) Brass is an alloy of zinc.
Explain, in terms of particles, why brass is harder than pure zinc…………………………………………………………………………………………………………………………….. [3]
▶️Answer/Explanation
Ans:
2(a) zinc blende
2(b)(i) $\begin{aligned} & \mathrm{ZnO}+\mathrm{C} \rightarrow \mathrm{Zn}+\mathrm{CO} \\ & \text { or } \\ & 2 \mathrm{ZnO}+\mathrm{C} \rightarrow 2 \mathrm{Zn}+\mathrm{CO}_2\end{aligned}$
2(b)(ii) chemical change: reduction (1)
explanation: oxygen is lost (1)
2(b)(iii) aluminium is more reactive than carbon
2(b)(iv) electrolysis
2(c) exists as layers (1)
(alloy) contains different sized (copper) atoms (1)
makes it more difficult for layers (of atoms) to slide over each slip/shift other (1)
Question
(a) Aqueous ammonium sulfate, $\left(\mathrm{NH}_4\right)_2 \mathrm{SO}_4$, is warmed with aqueous sodium hydroxide. The pungent-smelling gas ammonia, $\mathrm{NH}_3$, is produced. Balance the equation for this reaction.
$
\left(\mathrm{NH}_4\right)_2 \mathrm{SO}_4+\ldots . . \mathrm{NaOH} \rightarrow \ldots . . \mathrm{NH}_3+\ldots . . \mathrm{H}_2 \mathrm{O}+\mathrm{Na}_2 \mathrm{SO}_4
$
(b) A $2.8 \mathrm{~g}$ sample of impure ammonium sulfate is found to contain $0.7 \mathrm{~g}$ of impurities.
Calculate the percentage of ammonium sulfate in this sample.
percentage of ammonium sulfate $=$ $\%[1]$
(c) Describe a test for ammonia gas.
test………………………………………
result………………………………………[2]
(d) Ammonia gas is prepared at the front of a laboratory.
The pungent smell of ammonia spreads throughout the laboratory slowly.
(i) Name the process that occurs when ammonia gas spreads throughout the laboratory. [1]
(ii) Explain, using ideas about particles, why ammonia gas spreads throughout the laboratory.
(iii) Explain why carbon dioxide gas, $\mathrm{CO}_2$, will spread throughout the laboratory at a slower rate than ammonia gas, $\mathrm{NH}_3$.
(e) Ammonia is produced in the Haber process.
The equation for the reaction is shown.
$
\mathrm{N}_2(\mathrm{~g})+3 \mathrm{H}_2(\mathrm{~g}) \rightarrow 2 \mathrm{NH}_3(\mathrm{~g})
$
(i) In the Haber process, a temperature of $450^{\circ} \mathrm{C}$ and a pressure of 200 atmospheres are used in the presence of finely-divided iron.
A larger equilibrium yield of ammonia would be produced if a lower temperature and a higher pressure are used.
Explain why a lower temperature and a higher pressure are not used.
lower temperature…………………………………………………………………….
higher pressure………………………………………………………………………………[2]
(ii) State the role of iron in the Haber process.[1]
(f) Ammonia is a weak base.
(i) Explain the meaning of the term base.
(ii) Suggest the pH of aqueous ammonia………………………………………………………………………………………………………………………. [1] [Total: 13]
▶️Answer/Explanation
Ans:
3(a)(i) 2→ 2 + 2 1
3(b) 75(%) 1
3(c) test: (damp red) litmus paper (1)
result: (litmus goes) blue (1)
3(d)(i) diffusion 1
3(d)(ii) particles move from an area of high to low concentration
particles move randomly
3(d)(iii) $\mathrm{CO}_2$ molecules are heavier (than $\mathrm{NH}_3$ )
3(e)(i) lower temperature: (rate of reaction) slower (1)
higher pressure: expensive/specialist equipment
3(e)(ii) catalyst
3(f)(i) proton acceptor
3(f)(ii) any value greater than 7 up to 12
Question
Air is a mixture of gases.
(a) State the percentage of clean dry air which is oxygen. Give your answer to the nearest whole number.
$\%[1]$
(b) Oxygen and nitrogen are useful gases that can be obtained from air.
(i) Name the process used to separate oxygen and nitrogen from liquid air.[5]
(ii) State the property of oxygen and nitrogen that allows these gases to be separated using this process.[1]
(c) Carbon dioxide, $\mathrm{CO}_2$, is a covalent molecule. Complete the diagram to show the electron arrangement in one molecule of $\mathrm{CO}_2$.
Show only the outer electrons.
(d) The graph shows the concentration of carbon dioxide in the atmosphere over a 60‐year period, measured in parts per million (ppm).
The data shown in the graph is of global concern.
Explain why…………………………………………………………………………………………………………………………….. [3]
(e) Name the process in the carbon cycle by which plants remove carbon dioxide from the
atmosphere…………………………………………………………………………………………………………………………….. [1] [Total: 10]
▶️Answer/Explanation
Ans:
4(a) 21
4(b)(i) fractional (1)
distillation (1)
4(b)(ii) (different) boiling point 1
4(c) 2 double bonds (1)
whole molecule correct (2 pairs of lone pairs on each O) (1)
4(d) increase in (concentrations of) carbon dioxide
(carbon dioxide is) greenhouse gas/greenhouse effect
contributes to climate change/global warming
4(e) photosynthesis
Question
(a) Dilute sulfuric acid is electrolysed using the apparatus shown in the diagram.
(i) State what is meant by the term electrolysis.[2]
(ii) Explain why inert electrodes are used.[1]
(iii) Name the products formed at each electrode.
negative electrode……………………………………………..
positive electrode…………………………………………..[2]
(iv) Write an ionic half-equation for the reaction at the negative electrode.[2]
(b) Sulfuric acid is manufactured using the Contact process. This manufacture involves four stages.
(i) Stage 1 involves the combustion of sulfur to form sulfur dioxide.
Write the chemical equation for stage 1.[1]
(ii) The equation for stage 2 is shown.
$
2 \mathrm{SO}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{SO}_3(\mathrm{~g})
$
The reaction can reach equilibrium.
Explain what is meant by the term equilibrium.[2]
(iii) The energy level diagram for the forward reaction in stage 2 is shown.
[2]
Explain what the diagram shows about the energy changes in the forward reaction.
(c) In stage 3 sulfur trioxide, $\mathrm{SO}_3$, is converted to oleum, $\mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_7$.
In stage 4 oleum reacts to form sulfuric acid, $\mathrm{H}_2 \mathrm{SO}_4$.
State what oleum reacts with in stage 4 .[1]
(d) A sample of sulfuric acid, $\mathrm{H}_2 \mathrm{SO}_4$, has a concentration of $0.75 \mathrm{~mol} / \mathrm{dm}^3$.
Calculate the concentration of sulfuric acid in $\mathrm{g} / \mathrm{dm}^3$.
$\mathrm{g} / \mathrm{dm}^3[2]$[Total: 15]
▶️Answer/Explanation
Ans:
5(a)(i) breakdown by (the passage of) electricity (1)
of an ionic compound in molten/aqueous (state) (1)
5(a)(ii) they do not react 1
5(a)(iii) negative electrode: hydrogen (gas) (1)
positive electrode: oxygen (gas) (1)
5(a)(iv)
$\mathrm{H}^{+}+\mathrm{e}(-)$ as the only species on the left (1) equation fully correct (1)
$
2 \mathrm{H}^{+}+2 \mathrm{e}(-) \rightarrow \mathrm{H}_2 \text { (scores 2) }
$
5(b)(i) $\mathrm{S}+\mathrm{O}_2 \rightarrow \mathrm{SO}_2$
5(b)(ii) rate of forward reaction is equal to rate of reverse reaction (1)
constant concentration (of reactants and products) (1)
5(b)(iii) exothermic / heat / energy is released / surroundings warm up
products have lower energy than reactants / ORA
5(c) water / H2O
5(d) (Mr =) 98
(0.75× 98 =) 73.5
Question
(a) Ethane, propane and butane are members of the same homologous series.
(i) Name this homologous series.[1]
(ii) State two ways members of the same homologous series are similar.
1……………………………………………………………………………
2………………………………………………………………….[2]
(b) One mole of ethane, $\mathrm{C}_2 \mathrm{H}_6$, contains $6.02 \times 10^{23}$ molecules.
Calculate how many molecules are in $15 \mathrm{~g}$ of ethane.
number of ethane molecules $=$[1]
(c) Propane reacts with chlorine.
(i) Write the formula of the product which does not contain carbon. [1]
(ii) Draw the structure of an organic product formed. Show all of the atoms and all of the bonds.
(iii) State the name of this type of reaction. ……………………………………………………………………………………………………………………… [1]
(d) (i) Aqueous bromine was added to a sample of ethene.
Give the colour change seen.
from ……………………………………………………. to …………………………………………………… [2]
(ii) Explain, in terms of bonding, why there is no colour change when aqueous bromine is added to ethane………………………………………………………………………………………………………………………. [1]
(e) There are two structural isomers with the formula $\mathrm{C}_4 \mathrm{H}_{10}$.
(i) Draw the structures of both of these isomers, showing all of the atoms and all of the bonds.
(ii) Butane is formed when longer chain hydrocarbons are cracked.
Complete the chemical equation to show the other product when butane is formed by cracking.
$
\mathrm{C}_6 \mathrm{H}_{14} \rightarrow \mathrm{C}_4 \mathrm{H}_{10}+\ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots . . \cdots
$
(f) A compound contains $85.7 \%$ carbon and $14.3 \%$ hydrogen by mass.
(i) Calculate the empirical formula of this compound.
Show your working.[3]
(ii) The molecular mass of the compound is 112 .
Calculate the molecular formula of this compound.[1] [Total: 16]
▶️Answer/Explanation
Ans:
6(a)(i) alkanes 1
6(a)(ii) one mark each for any two of:
• same chemical properties
• same functional group
• same general formula
• (consecutive members) differ by CH2
• common (allow similar) methods of preparation
• physical properties vary in predictable manner / show trends / gradually change OR example of a physical property
variation i.e. melting point / boiling point / volatility (1)
6(b) $3.01 \times 10^{23}$ (molecules)
6(c)(i) HCl
6(c)(ii)
6(c)(ii) substitution 1
6(d)(i) from: orange (1)
to: colourless (1)
6(d)(ii) contains no double bonds/ethane only contains single bonds
6(e)(i)
6(e)(ii) $\mathrm{C}_2 \mathrm{H}_4$
6(f)(i) $\begin{aligned} & \left(\mathrm{C}=85.7, \mathrm{H}=14.3, M_{\mathrm{r}} 112\right) \\ & \mathrm{C}=\frac{85.7}{12}=7.14 \quad \mathrm{H}=\frac{14.3}{1}=14.3(1) \\ & (\text { ratio }=7.13: 14.3=1: 2) \\ & \mathrm{CH}_2(2)\end{aligned}$
6(f)(ii) $\mathrm{C}_6 \mathrm{H}_{16}$
Question
(a) Ethanol can be manufactured by two different methods.
Method 1: fermentation of a sugar, $\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6$
$
\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6 \rightarrow 2 \mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}+2 \mathrm{CO}_2
$
Method 2: reaction of ethene with steam
$
\mathrm{C}_2 \mathrm{H}_4+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}
$
(i) Give one advantage of using fermentation compared with Method 2.[1]
(ii) Give one disadvantage of using fermentation compared with Method 2.[1]
(b) Ethanol reacts with acidified potassium manganate(VII) to form water and a product that turns litmus red.
(i) State the name of the product that turns the litmus red.[1]
(ii) State the type of reaction that ethanol undergoes when it reacts with acidified potassium manganate(VII).[1]
(c) Ethanol reacts with methanoic acid to form an ester.
(i) Name the ester formed in this reaction. ……………………………………………………………………………………………………………………… [1]
(ii) Draw the structure of the ester formed.
Show all of the atoms and all of the bonds.
(d) The table shows the melting points of ethanol and sodium chloride.
The difference in melting points is due to differences in attractive forces between particles in these substances.
Name the type of attractive force in each substance, which is responsible for the difference in melting points.
ethanol ………………………………………………………………………………………………………………………
sodium chloride ………………………………………………………………………………………………………….[2] [Total: 8]
▶️Answer/Explanation
Ans:
7(a)(i) sugar or $\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6$, is renewable/ sustainable
7(a)(ii) slow(er) process
7(b)(i) ethanoic acid
7(b)(ii) oxidation
7(c)(i) ethyl methanoate
7(c)(ii)
7(d) ethanol: (forces of attraction) between molecules (1)
sodium chloride: (force of attraction) between positive and negative ions/ionic bonding (1)