Chemistry 5070/42 — May/June 2011

Cambridge O-Level · Alternative to Practical · worked solutions for every part, with the mark scheme

questions

marks

minutes

Topics Experimental Contexts · Analysis, Conclusions and Evaluation · Observations and Measurements · Qualitative Analysis · Use of Techniques, Apparatus and Materials

Q110MObservations and MeasurementsExperimental ContextsAnalysis, Conclusions and EvaluationFree sample

A student adds hydrochloric acid to calcium carbonate to produce carbon dioxide.

Fig. 1.1

The diagram below shows the gas syringe containing the volume of carbon dioxide collected in one minute.

Fig. 1.2

(a)

What volume of carbon dioxide is collected in one minute?

______ $\text{cm}^3$

(b)

Will the volume collected during the second minute be less than, the same, or more than the volume collected during the first minute? Explain your answer.

______

(c)

The equation for the reaction is

\text{CaCO}_3 + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2

$50\text{ cm}^3$ of $0.20\text{ mol/dm}^3$ hydrochloric acid is added to an excess of calcium carbonate.

(i)

Calculate the number of moles in $50\text{ cm}^3$ of $0.20\text{ mol/dm}^3$ hydrochloric acid.

______ moles

(ii)

Calculate the relative formula mass of calcium carbonate.
[ $A_r$ : C, 12; O, 16; Ca, 40.]

______

(iii)

Using your answers to (c)(i) and (c)(ii) and the equation for the reaction, calculate the mass of calcium carbonate required to completely react with $50\text{ cm}^3$ of $0.20\text{ mol/dm}^3$ hydrochloric acid.

______ $\text{cm}^3$

(iv)

Calculate the maximum volume of carbon dioxide that is produced when $50\text{ cm}^3$ of $0.20\text{ mol/dm}^3$ of hydrochloric acid reacts completely with the excess calcium carbonate.
[1 mole of a gas occupies a volume of $24\text{ dm}^3$ at room temperature and pressure.]

______ $\text{cm}^3$

(d)

Suggest how the speed of this reaction can be increased by changing

(i)

the particle size of calcium carbonate,

______

(ii)

the concentration of hydrochloric acid.

______

(e)

Suggest another way in which the student can increase the speed of the reaction.

______

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Q8Experimental Contexts · Observations and Measurements · Analysis, Conclusions and Evaluation · Use of Techniques, Apparatus and Materials13M
Q9Qualitative Analysis · Experimental Contexts10M
Q10Experimental Contexts · Observations and Measurements · Analysis, Conclusions and Evaluation12M

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