Chemistry 9701/32 — May/June 2019

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

questions

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

Quantitative analysis

Read through the whole method before starting any practical work. Where appropriate, prepare a table for your results in the space provided.

Show the precision of the apparatus you used in the data you record.

Show your working and appropriate significant figures in the final answer to each step of your calculations.

Amidosulfonic acid is a monoprotic acid with the formula $\text{HSO}_x\text{NH}_2$ . In this experiment you will determine the value of $x$ in the formula by titration with an alkali.

FB 1 is amidosulfonic acid, $\text{HSO}_x\text{NH}_2$ . You are supplied with approximately $3.0\text{ g}$ .
FB 2 is $0.110\text{ mol dm}^{-3}$ sodium hydroxide, $\text{NaOH}$ .
thymolphthalein indicator

(a)

Method

Preparing a solution of amidosulfonic acid

Weigh the empty beaker. Record the mass.
Add $2.50\text{--}2.70\text{ g}$ of FB 1 to the beaker. Weigh the beaker and its contents. Record the mass.
Calculate and record the mass of FB 1 used.
Add approximately $100\text{ cm}^3$ of distilled water to the beaker and stir to dissolve FB 1.
Transfer the solution to the $250\text{ cm}^3$ volumetric flask.
Rinse the beaker twice with approximately $20\text{ cm}^3$ of distilled water each time and add to the volumetric flask.
Add distilled water to the volumetric flask to make $250\text{ cm}^3$ of solution.
Shake the volumetric flask to mix the solution thoroughly and label it FB 3.

Titration of FB 3

Fill the burette with FB 2.
Pipette $25.0\text{ cm}^3$ of FB 3 into a conical flask.
Add a few drops of thymolphthalein to the conical flask.
Carry out a rough titration.
Record your burette readings and the rough titre in the space below.

The rough titre is .............................. $\text{cm}^3$ .

Carry out as many accurate titrations as you think necessary to obtain consistent results.
Make sure any recorded results show the precision of your practical work.
Record all of your burette readings and the volume of FB 2 added in each accurate titration.

(b)

From your accurate titration results, obtain a suitable value for the volume of FB 2 to be used in your calculations.
Show clearly how you obtained this value.

$25.0\text{ cm}^3$ of FB 3 required .............................. $\text{cm}^3$ of FB 2.

(c)

Calculations

(i)

Give your answers to (ii), (iii), (iv) and (v) to the appropriate number of significant figures.

(ii)

Calculate the number of moles of sodium hydroxide, $\text{NaOH}$ , in the volume of FB 2 calculated in (b).

\text{moles of NaOH} = .............................. \text{ mol}

(iii)

One mole of sodium hydroxide neutralises one mole of amidosulfonic acid.

Complete the equation for the reaction of amidosulfonic acid with sodium hydroxide. Include state symbols.

......\text{NaOH}...... + ......\text{HSO}_x\text{NH}_2...... \rightarrow ................................. + .................................

State the number of moles of amidosulfonic acid that reacted with the number of moles of $\text{NaOH}$ calculated in (ii).

\text{moles of HSO}_x\text{NH}_2 = .............................. \text{ mol}

(iv)

Use your results on page 2 and your answer to (iii) to calculate the relative formula mass, $M_r$ , of amidosulfonic acid.

M_r \text{ of amidosulfonic acid} = ..............................

(v)

Calculate the value of $x$ in the formula of amidosulfonic acid, $\text{HSO}_x\text{NH}_2$ .

x = ..............................

(d)

The salts produced from amidosulfonic acid are called amidosulfonates.

You are to carry out an experiment using FB 1 to find out if barium amidosulfonate is soluble in water.

Describe your experiment.
Record your observation(s) and conclusion.

The rest of this paper

2 more questions

Q2Manipulation, Measurement and Observation · Presentation of Data and Observations · Analysis, Conclusions and Evaluation10M
Q3Qualitative Analysis · Manipulation, Measurement and Observation · Analysis, Conclusions and Evaluation · Presentation of Data and Observations14M

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