Edexcel IGCSE Chemistry Standard-form Numbers

Edexcel IGCSE Chemistry Standard-form Numbers
Edexcel IGCSE Chemistry syllabusChemistry 4CH1Issue 3 (2024)

Practise Edexcel IGCSE Chemistry standard-form numbers by calculating reaction rate from time and converting the value to standard form.

How this is tested

  • Calculate a reaction rate from one divided by time and convert the decimal to standard form.

Question 4(c)

[Maximum number: 2]

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 cm325 \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.

Use information from the table to calculate the mean rate of reaction at 20∘C20^{\circ} \mathrm{C}.

Use the expression

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

Give your answer in standard form.
mean rate =