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9701/53

Chemistry 9701/53 — October/November 2013

Cambridge A-Level · Planning, Analysis and Evaluation · worked solutions for every part, with the mark scheme

3
questions
30
marks
75
minutes

Topics Analysis, Conclusions and Evaluation · Planning

Q1Analysis, Conclusions and EvaluationPlanningFree sample

Air, which is 99% nitrogen and oxygen, is slightly soluble in water. At 25 °C a saturated solution of air in water has a concentration of 19 cm³ dm⁻³. When water is boiled all the dissolved air is boiled out of solution.

(a)
4M
(i)

The molar enthalpies of solution for nitrogen and oxygen are:

ΔHsoln N2=−1.04 kJ mol−1andΔHsoln O2=−1.20 kJ mol−1\Delta H_{\text{soln}} \text{ N}_2 = -1.04 \text{ kJ mol}^{-1} \quad \text{and} \quad \Delta H_{\text{soln}} \text{ O}_2 = -1.20 \text{ kJ mol}^{-1}

Predict how the solubility of air in water will change as the temperature is increased. Explain this prediction using Le Chatelier’s principle in terms of the equilibrium between air and the aqueous solution as the temperature is increased.

Prediction ...................................................................................................................

Explanation ....................................................................................................................

(ii)

Display your prediction in the form of a sketch graph for the solubility of air between 0 °C and 100 °C, labelling clearly the axes. Include labelled points to indicate the solubility of air at 25 °C and 100 °C.

(b)

If you were to carry out an experiment to investigate how the solubility of air varies as the temperature increases name,

1M
(i)

the independent variable,

(ii)

the dependent variable.

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2 more questions
  • Q2Planning · Analysis, Conclusions and Evaluation10M
  • Q3Analysis, Conclusions and Evaluation15M
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