Question
Some elements are shown in the order they appear in the reactivity series. The most reactive element is at the top.
sodium
calcium
magnesium
aluminium
zinc
iron
hydrogen
copper
(a) Answer the questions using the list of elements. Each element may be used once, more than once or not at all.
Identify:
(i) a non-metal
(ii) a metal which is stored under oil
(iii) the main component of steel
(iv) a metal with three electrons in the outer shell of its atoms
(v) a metal found in brass
(vi) a metal that forms chlorides of the type \(XCl_2\) and \(XCl_3\).
(b) Name the main ores of:
(i) zinc ……………………………………………………………………………………………………………….
(ii) aluminium. ……………………………………………………………………………………………………..
(c) In an experiment, a sample of aluminium appeared less reactive than expected.
Explain why.
(d) Name two metals from the list which are extracted by reduction of their ores using carbon.
1 ……………………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………………….
(e) When zinc granules are added to aqueous copper(II) sulfate, a reaction occurs. During the
reaction, a red-pink solid is formed and the solution becomes colourless.
(i) Name the red-pink solid.
(ii) Name the colourless solution.
(iii) Explain, in terms of particles, why the rate of this reaction increases when the temperature
is increased.
(iv) Suggest two other ways of increasing the rate of this reaction.
1 …………………………………………………………………………………………………………………………
2 …………………………………………………………………………………………………………………………
Answer/Explanation
Answer:
(a) (i) hydrogen
(ii) sodium
(iii) iron
(iv) aluminium
(v) zinc or copper
(vi) iron
(b) (i) zinc blende
(ii) bauxite
(c) protective oxide layer
(d) Any 2 from 3
• zinc
• iron
• copper
(e) (i) copper
(ii) zinc sulfate
(iii)
M1 particles have more energy
M2 More collisions (between particles) occur per second / per unit time
M3 A greater percentage / proportion / fraction of collisions (of particles) are successful / have energy above activation
energy / have energy equal to activation energy
(iv) Any 2 from 3:
• use a catalyst
• use smaller granules
• increase concentration
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
This question is about reactions of bases and acids.
(a) Ammonia is a gas at room temperature.
What is the test for ammonia gas? Describe the positive result of this test.
test…………………
result…………………..[2]
(b) Ammonia reacts with water to form ions.
$
\mathrm{NH}_3+\mathrm{H}_2 \mathrm{O} \rightleftharpoons \mathrm{NH}_4^{+}+\mathrm{OH}^{-}
$
(i) How does this equation show that ammonia, $\mathrm{NH}_3$, behaves as a base? [1]
(ii) Aqueous ammonia is described as a weak base.
Suggest the $\mathrm{pH}$ of aqueous ammonia.
$
\mathrm{pH}=
$
(iii) Describe what is seen when aqueous ammonia is added to aqueous copper(II) sulfate, until no further change is seen. [3]
(c) Aqueous sodium hydroxide, $\mathrm{NaOH}(\mathrm{aq})$, is a strong alkali that reacts with dilute sulfuric acid exothermically.
(i) What type of reaction is this? [1]
(ii) Complete the equation for the reaction between aqueous sodium hydroxide and dilute sulfuric acid.
$ 2 \mathrm{NaOH}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow $ → ……………………. + …………………….
(d) A student wanted to find the concentration of some dilute sulfuric acid by titration. The student found that $25.0 \mathrm{~cm}^3$ of $0.0400 \mathrm{~mol} / \mathrm{dm}^3 \mathrm{NaOH}(\mathrm{aq})$ reacted exactly with $20.0 \mathrm{~cm}^3$ of $\mathrm{H}_2 \mathrm{SO}_4(\mathrm{aq})$.
(i) Name a suitable indicator to use in this titration. [1]
(ii) Calculate the concentration of the $\mathrm{H}_2 \mathrm{SO}_4(\mathrm{aq})$ in $\mathrm{mol} / \mathrm{dm}^3$ using the following steps.
- Calculate the number of moles of $\mathrm{NaOH}$ in $25.0 \mathrm{~cm}^3$.
moles = …………………………
- Deduce the number of moles of $\mathrm{H}_2 \mathrm{SO}_4$ that reacted with the $25.0 \mathrm{~cm}^3$ of $\mathrm{NaOH}(\mathrm{aq})$.
moles $=$
Calculate the concentration of $\mathrm{H}_2 \mathrm{SO}_4(\mathrm{aq})$ in $\mathrm{mol} / \mathrm{dm}^3$.concentration $=$ $\mathrm{mol} / \mathrm{dm}^3$ [3]
(iii) Calculate the concentration of the $0.0400 \mathrm{~mol} / \mathrm{dm}^3 \mathrm{NaOH}(\mathrm{aq})$ in $\mathrm{g} / \mathrm{dm}^3$.
concentration $=$ $\mathrm{g} / \mathrm{dm}^3[2]$ [Total: 16]
▶️Answer/Explanation
Ans:
4(a) (damp) litmus
(turns) blue
4(b)(i) proton acceptor
4(b)(ii) Above pH 7 up to
4(b)(iii) blue precipitate
precipitate dissolves
deep blue solution remains
4(c)(i) neutralisation
4(c)(ii) $\mathrm{Na}_2 \mathrm{SO}_4$
$2 \mathrm{H}_2 \mathrm{O}$
4(d)(i) methyl orange
4(d)(ii) $\mathrm{M} 1 \mathrm{~mol}$ of $\mathrm{NaOH}=0.0400 \times \frac{25.0}{1000}=0.001(00) \mathrm{mol}$
$\mathrm{M} 2 \mathrm{~mol}$ of $\mathrm{H}_2 \mathrm{SO}_4=\frac{\mathrm{M} 1}{2}=\frac{0.001}{2}=0.0005(00)$
$\mathrm{M} 3 \mathrm{M} 2 \times \frac{1000}{20.0}=0.0005 \times \frac{1000}{20.0}=0.025\left(\mathrm{~mol} / \mathrm{dm}^3\right)$
allow ecf
4(d)(iii) M1 use of $40 \mathrm{~g} / \mathrm{mol}$ M2 $40 \times 0.04=1.6\left(\mathrm{~g} / \mathrm{dm}^3\right)$