AI SearchTopicalsYearlysNotesDashboardPricing
9701/34

Chemistry 9701/34 — May/June 2022

Cambridge AS Level · Advanced Practical Skills · worked solutions for every part, with the mark scheme

3
questions
40
marks
120
minutes

Topics Manipulation, Measurement and Observation · Presentation of Data and Observations · Analysis, Conclusions and Evaluation · Qualitative Analysis

Q1Manipulation, Measurement and ObservationPresentation of Data and ObservationsAnalysis, Conclusions and EvaluationFree sample

Calcium carbonate reacts with hydrochloric acid to release carbon dioxide.

CaCO3(s)+2HCl(aq)→CaCl2(aq)+CO2(g)+H2O(l)\text{CaCO}_3(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{CaCl}_2(\text{aq}) + \text{CO}_2(\text{g}) + \text{H}_2\text{O}(\text{l})

The concentration of the hydrochloric acid can be determined by reacting it with calcium carbonate and measuring the volume of carbon dioxide formed.

FB 1 is hydrochloric acid, HCl\text{HCl}.
FB 2 is calcium carbonate, CaCO3\text{CaCO}_3.

(a)

Method

  • Fill the tub with tap water to a depth of approximately 5 cm5\text{ cm}.
  • Fill the 250 cm3250\text{ cm}^3 measuring cylinder completely with water. Hold a piece of paper towel firmly over the top, invert the measuring cylinder and place it in the water in the tub.
  • Remove the paper towel and clamp the inverted measuring cylinder so the open end is in the water just above the base of the tub.
  • Using the 50 cm350\text{ cm}^3 measuring cylinder, transfer 50 cm350\text{ cm}^3 of FB 1 into the flask. Check that the bung fits tightly into the neck of the flask, clamp the flask and place the end of the delivery tube into the inverted 250 cm3250\text{ cm}^3 measuring cylinder.
  • Remove the bung from the neck of the flask. Tip all the FB 2, from the container, into the acid in the flask and replace the bung immediately. Remove the flask from the clamp and swirl it to mix the contents.
  • Replace the flask in the clamp. Leave for several minutes, swirling the flask occasionally.

You may wish to start Question 3 while the gas is being produced.

  • When the reaction stops producing gas, record the final volume of gas in the measuring cylinder.

Keep the flask and contents for use in 1(c)(i).

volume of gas = .............................. cm3\text{cm}^3

2M
(b)
(i)

Calculate the amount, in mol, of carbon dioxide collected in the measuring cylinder.
(Assume that 1 mol1\text{ mol} of gas occupies 24.0 dm324.0\text{ dm}^3 under these conditions.)

amount of CO2\text{CO}_2 = .............................. mol

1M
(ii)

Use your answer to (b)(i) and the equation on page 2 to calculate the concentration, in mol dm−3\text{mol dm}^{-3}, of hydrochloric acid in FB 1. Show your working.

concentration of HCl\text{HCl} = .............................. mol dm−3\text{mol dm}^{-3}

2M
(c)
(i)

A student thinks that the mass of FB 2 should be measured.

Explain, by observing the contents of the flask, why this is not necessary.

2M
(ii)

In this experiment some carbon dioxide is lost before the bung is replaced.

Suggest a change that could be made to minimise the loss of gas. Explain how this change minimises the loss of gas.

1M

The rest of this paper

2 more questions
  • Q2Manipulation, Measurement and Observation · Presentation of Data and Observations · Analysis, Conclusions and Evaluation17M
  • Q3Manipulation, Measurement and Observation · Presentation of Data and Observations · Analysis, Conclusions and Evaluation · Qualitative Analysis15M
Loading the full paper…