A student investigates a sample of rock salt. The student: - grinds the rock salt into a powder - places the powder into a beaker and adds water to it - stirs the mixture - pours the mixture through the apparatus shown. (i) Name apparatus A. \_\_\_\_\_\_ (ii) Name apparatus B. \_\_\_\_\_\_ (iii) A brown solid remains in apparatus A. A colourless solution is collected in apparatus B. Name the process used to separate the solid from the colourless solution. \_\_\_\_\_\_ (b)…

Chemistry 5070/41 — May/June 2020

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

questions

marks

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

Q112MUse of Techniques, Apparatus and MaterialsExperimental ContextsQualitative AnalysisObservations and MeasurementsPlanning Experiments and InvestigationsAnalysis, Conclusions and EvaluationFree sample

A student investigates a sample of rock salt.

The student:

grinds the rock salt into a powder
places the powder into a beaker and adds water to it
stirs the mixture
pours the mixture through the apparatus shown.

Fig. 1.1

(a)

(i)

Name apparatus A.

______

(ii)

Name apparatus B.

______

(iii)

A brown solid remains in apparatus A. A colourless solution is collected in apparatus B.

Name the process used to separate the solid from the colourless solution.

______

(b)

The colourless solution contains two different cations. One cation is sodium.

The student adds dilute nitric acid and aqueous sodium sulfate to the colourless solution.

A white precipitate is formed.

Name the other cation in the colourless solution.

______

(c)

A student investigates the effect of adding different masses of rock salt on the temperature of a mixture of ice and water.

The diagram shows the volume of water the student uses in the investigation.

Fig. 1.2

State the volume of water the student uses. = ______ $\text{cm}^3$

(d)

The student:

places the water in a beaker
adds ice
stirs the mixture
measures the lowest temperature of the mixture
repeats the experiment four times.

In each of the repeated experiments a different mass of rock salt is added to the mixture.

(i)

State a variable that needs to be kept constant in each experiment.

______

(ii)

The diagram shows part of the thermometer the student uses to measure the lowest temperature reached when $1.0\text{ g}$ of rock salt is added.

Fig. 1.3

Record this temperature in the table of results.

mass of rock salt added / $\text{g}$	lowest temperature of ice and salt mixture / $^\circ\text{C}$
0.0	0.0
0.5	–1.9
1.0
1.5	–5.8
2.0	–7.8

(iii)

Plot the results on the grid.

Include:

a suitable scale for the x-axis
a straight line of best fit.

Fig. 1.4

(iv)

Use your graph to find the lowest temperature when $1.4\text{ g}$ of rock salt is added.

______ $^\circ\text{C}$

(v)

Deduce the relationship between the mass of rock salt added and the lowest temperature reached.

______

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Q3Planning Experiments and Investigations · Experimental Contexts · Observations and Measurements5M
Q4Qualitative Analysis · Observations and Measurements12M
Q5Experimental Contexts · Use of Techniques, Apparatus and Materials · Analysis, Conclusions and Evaluation14M
Q6Experimental Contexts · Observations and Measurements · Analysis, Conclusions and Evaluation5M

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