FA 1 is an aqueous solution of hydrochloric acid, $\text{HCl}$. FA 2 is aqueous sodium hydroxide containing $10.00\text{ g dm}^{-3}$ $\text{NaOH}$. You are to determine the concentration, in $\text{mol dm}^{-3}$, of the hydrochloric acid in FA 1 . (a) Method Fill a burette with FA 2 . Pipette $10.0\text{ cm}^3$ of FA 1 into a conical flask. Add to the flask a few drops of the acid-base indicator provided. Place the flask on a white tile. Titrate the acid in the flask with FA…

Chemistry 9701/35 — October/November 2010

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

FA 1 is an aqueous solution of hydrochloric acid, $\text{HCl}$ .
FA 2 is aqueous sodium hydroxide containing $10.00\text{ g dm}^{-3}$ $\text{NaOH}$ .

You are to determine the concentration, in $\text{mol dm}^{-3}$ , of the hydrochloric acid in FA 1.

(a)

Method

Fill a burette with FA 2.
Pipette $10.0\text{ cm}^3$ of FA 1 into a conical flask.
Add to the flask a few drops of the acid-base indicator provided.
Place the flask on a white tile.
Titrate the acid in the flask with FA 2.

You should perform a rough titration.
In the space below record your burette readings for this rough titration.

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

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

(b)

From your titration results obtain a suitable value to be used in your calculation.
Show clearly how you have obtained this value.

$10.0\text{ cm}^3$ of FA 1 required ................................. $\text{cm}^3$ of FA 2.

(c)

Calculations

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

(i)

Calculate the concentration, in $\text{mol dm}^{-3}$ , of the sodium hydroxide in FA 2.

FA 2 contains $10.00\text{ g dm}^{-3}$ $\text{NaOH}$ .
[ $A_r$ : $\text{H}, 1.0$ ; $\text{O}, 16.0$ ; $\text{Na}, 23.0$ ]

The concentration of sodium hydroxide in FA 2 is ...................................... $\text{mol dm}^{-3}$ .

(ii)

Calculate how many moles of sodium hydroxide are contained in the volume recorded in (b).

................................................................. $\text{mol of NaOH}$ .

(iii)

Deduce how many moles of hydrochloric acid were pipetted into the conical flask and calculate the concentration, in $\text{mol dm}^{-3}$ , of the hydrochloric acid in FA 1.

\text{NaOH(aq)} + \text{HCl(aq)} \rightarrow \text{NaCl(aq)} + \text{H}_2\text{O(l)}

The concentration of the hydrochloric acid in FA 1 is ...................................... $\text{mol dm}^{-3}$ .

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2 more questions

Q2Presentation of Data and Observations · Manipulation, Measurement and Observation · Analysis, Conclusions and Evaluation14M
Q3Qualitative Analysis16M

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