Question
Give the name of the process that is used:
(a) to produce ammonia from nitrogen
(b) to separate nitrogen from liquid air
(c) to produce bromine from molten lead(II) bromide
(d) to separate an undissolved solid from an aqueous solution
(e) to produce amino acids from proteins
(f) to separate a mixture of amino acids.
Answer/Explanation
Answer:
(a) Haber (process)
(b) fractional distillation
(c) electrolysis
(d) filtration
(e) hydrolysis
(f) chromatography
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
(a) Sulfuric acid is made industrially by a four-step process.
step 1 Sulfur is burned in air to produce sulfur dioxide.
step 2 Sulfur dioxide is converted into sulfur trioxide.
step 3 Sulfur trioxide is reacted with concentrated sulfuric acid to produce oleum.
step 4 Oleum is reacted with water to produce concentrated sulfuric acid.
(i) Some sulfur is obtained by mining. Name one other major source of sulfur.
.…………………………………………………………………………………………………………………….. [1]
(ii) What is the name of the process by which sulfuric acid is made industrially?
……………………………………………………………………………………………………………………… [1]
(iii) Describe the conversion of sulfur dioxide into sulfur trioxide in step 2. In your answer, include:
● a chemical equation for the reaction
● the essential reaction conditions.
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………… [5]
(b) When concentrated sulfuric acid is added to glucose, C6H12O6, a black solid is produced. The concentrated sulfuric acid acts as a dehydrating agent.
(i) What is removed from the glucose in this reaction?
……………………………………………………………………………………………………………………… [1]
(ii) Name the black solid produced in this reaction.
……………………………………………………………………………………………………………………… [1]
(c) The gas hydrogen sulfide, H2S, is produced when concentrated sulfuric acid is added to solid
potassium iodide.
The reaction involves oxidation.
(i) Define the term oxidation in terms of electron transfer.
……………………………………………………………………………………………………………………… [1]
(ii) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of
hydrogen sulfide. Show outer shell electrons only.
[2]
(iii) Hydrogen sulfide has a simple molecular structure. Explain why hydrogen sulfide has a low boiling point.
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………… [2]
(d) Dilute sulfuric acid reacts with aqueous sodium hydrogencarbonate in a neutralisation reaction.
\( H_2SO_4(aq) + 2NaHCO_3(aq) \rightarrow Na_2SO_4\)(aq) +\(2H_2O(l) + 2CO_2\)(g)
In a titration, 0.200mol/\(dm^{3}\) aqueous sodium hydrogencarbonate was used to neutralise \(20.0cm^{3}\) of dilute sulfuric acid of concentration 0.150mol/\(dm^{3}\) .
(i) Calculate the number of moles of dilute sulfuric acid used in the titration.
………………………… mol [1]
(ii) Calculate the number of moles of sodium hydrogencarbonate needed to neutralise the dilute sulfuric acid.
………………………… mol [1]
(iii) Calculate the volume, in \(cm^{3}\) , of 0.200mol/\(dm^{3}\) aqueous sodium hydrogencarbonate needed to neutralise the dilute sulfuric acid.
………………………… \(cm^3\) [1] [Total: 17]
Answer/Explanation
4(a)(i) from petroleum or (crude) oil or fossil fuels
4(a)(ii) Contact (process)
4(a)(iii) M1 vanadium pentoxide or vanadium(V) oxide or V2O5 (catalyst);
M2 1–5 atmospheres; (Units required)
M3 450°C; units required
\(M_4 2SO_2 + O_2\rightarrow 2SO_3 \);
M5 equilibrium / reversible reaction in equation or text
4(b)(i) water / \(H_2O\)
4(b)(ii) carbon / C
4(c)(i) (oxidation is) loss of electrons
4(c)(ii) M1 one shared pair between each H and S
M2 four unpaired electrons on S giving S a total of 8 outer shell electrons and no other unpaired electrons
4(c)(iii) M1 weak (attractive) forces OR (attractive) forces need little energy to overcome
M2 forces between molecules / intermolecular
4(d)(i) 0.003
4(d)(ii) 0.006
4(d)(iii) 30