Edexcel IGCSE Chemistry Mathematical Skills

Practise Edexcel IGCSE Chemistry mathematical skills by using graphs, gradients, reaction rates, gas volumes and clear working.

[Maximum number: 6]

A student investigates the effect of temperature on the rate of reaction between two solutions, A and B . When the reaction occurs, the mixture turns from colourless to blue.

This is the student's method.
- pour $25 \mathrm{~cm}^{3}$ of solution A into a conical flask
- add solution B and measure the temperature of the mixture
- record the time taken for the mixture to turn blue

The student repeats this method at different temperatures.

(a)

The table shows the student's results.

Table for Question (a) — Edexcel IGCSE Chemistry

[ 4 ]

(i)

Plot the student's results on the grid.

[ 1 ]

(ii)

Draw a curve of best fit.

Figure for Question (ii) — Edexcel IGCSE Chemistry

[ 1 ]

(iii)

Use your graph to determine the time taken for the mixture to turn blue at $55^{\circ} \mathrm{C}$ .

Show your working on the graph.
time taken = s

[ 2 ]

(b)

Use information from the table to calculate the mean rate of reaction at $20^{\circ} \mathrm{C}$ .

Use the expression

\text { mean rate }=\frac{1}{\text { time in seconds }}

Give your answer in standard form.
mean rate =

[ 2 ]

M1 $\frac{1}{156}$ OR 0.00641

M2 $\quad 6.41 \times 10^{-3}$

ALLOW use of value from graph

ALLOW $6.4 \times 10^{-3}$

[Maximum number: 2]

This question is about displacement reactions.

A student uses this method to investigate what happens when excess metal is added to a solution of copper(II) sulfate.
- pour some copper(II) sulfate solution into a polystyrene cup and record the temperature
- add excess metal W to the polystyrene cup and stir the mixture
- record the maximum temperature reached
- calculate the temperature increase of the solution

The student repeats the method for metals X, Y and Z.
For each metal, the student records three sets of results.

The table shows the student's results.

Table for Question 6 Mathematical skills question 2 — Edexcel IGCSE Chemistry

Calculate the mean temperature increase for metal Y.

Give your answer to two significant figures.
mean temperature increase = ${ }^{\circ} \mathrm{C}$

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Covered syllabus points

6 Mathematical skills question 1

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (b)

6 Mathematical skills question 2