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9701/41

Chemistry 9701/41 — October/November 2021

Cambridge A-Level · A Level Structured Questions · worked solutions for every part, with the mark scheme

10
questions
100
marks
120
minutes

Topics Chemical Energetics · Nitrogen Compounds · Electrochemistry · Hydrocarbons · Transition Elements · Analytical Techniques · +5 more

Q1ElectrochemistryChemical EnergeticsFree sample

When dilute sulfuric acid is electrolysed, water is split into hydrogen and oxygen.

2H2O(l)→2H2(g)+O2(g)2\text{H}_2\text{O(l)} \rightarrow 2\text{H}_2\text{(g)} + \text{O}_2\text{(g)}

A current of x Ax\text{ A} is passed through the solution for 14.0 minutes. 462 cm3462\text{ cm}^3 of hydrogen are produced at the cathode, measured under room conditions.

(a)

Calculate the number of hydrogen molecules produced during the electrolysis.

2M
(b)

Calculate the total number of electrons transferred to produce this number of hydrogen molecules.

1M
(c)

Calculate the quantity of charge, in coulombs, of the total number of electrons calculated in (b).

1M
(d)

Calculate the current, xx, passed during this experiment.

1M
(e)

The standard entropies, S⊖S^\ominus, of three species are given in the table.

speciesS⊖/J K−1mol−1S^\ominus / \text{J K}^{-1}\text{mol}^{-1}
H2O(l)\text{H}_2\text{O(l)}+70+70
H2(g)\text{H}_2\text{(g)}+131+131
O2(g)\text{O}_2\text{(g)}+205+205
(i)

Calculate ΔS⊖\Delta S^\ominus for the reaction 2H2O(l)→2H2(g)+O2(g)2\text{H}_2\text{O(l)} \rightarrow 2\text{H}_2\text{(g)} + \text{O}_2\text{(g)}.

1M
(ii)

ΔH⊖\Delta H^\ominus for the reaction 2H2O(l)→2H2(g)+O2(g)2\text{H}_2\text{O(l)} \rightarrow 2\text{H}_2\text{(g)} + \text{O}_2\text{(g)} is +572 kJ mol−1+572\text{ kJ mol}^{-1}.

Calculate ΔG⊖\Delta G^\ominus for this reaction at 298 K298\text{ K}.

2M
(iii)

Predict the effect of increasing temperature on the spontaneity of this reaction.
Explain your answer.

1M

The rest of this paper

9 more questions
  • Q2Equilibria10M
  • Q3Chemical Energetics12M
  • Q4Group 2 · Chemical Energetics · Hydrocarbons8M
  • Q5Transition Elements14M
  • Q6Transition Elements · Electrochemistry10M
  • Q7Analytical Techniques · Carboxylic Acids and Derivatives · Hydroxy Compounds · Hydrocarbons · Halogen Compounds14M
  • Q8Nitrogen Compounds5M
  • Q9Carboxylic Acids and Derivatives · Nitrogen Compounds · Analytical Techniques12M
  • Q10Nitrogen Compounds6M
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