A student repeats a sodium thiosulfate and hydrochloric acid experiment four times under the same conditions. The times for the cross to disappear are 42 s, 45 s, 61 s and 43 s.
The student ignores any anomalous result, calculates the mean time and then uses rate=1mean time\displaystyle \mathrm{rate} = \frac{1}{\text{mean time}}rate=mean time1.
What value of the rate does the student get?
0.0164 s−10.0164\,\mathrm{s^{-1}}0.0164s−1
0.0209 s−10.0209\,\mathrm{s^{-1}}0.0209s−1
0.0231 s−10.0231\,\mathrm{s^{-1}}0.0231s−1
0.0238 s−10.0238\,\mathrm{s^{-1}}0.0238s−1
54 exam-style questions on Edexcel GCSE Chemistry 8.1 Rates of reaction, covering 8.1.1 Measuring and interpreting rates of reaction, 8.1.2 Collision theory and the factors affecting rate, and 8.1.3 Catalysts and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.