A student investigates the temperature change during the displacement reaction between copper(II) sulfate solution and zinc powder.
The student places 50 cm3 of copper(II) sulfate solution in a reaction vessel and adds zinc powder in 0.5 g portions, recording the temperature of the mixture after each addition and stirring.
Explain how wrapping the reaction vessel in cotton wool improves the accuracy of the temperature measurements.
The results of the experiment are shown below:
Mass of zinc added (g)Temperature (∘C)0.018.20.521.61.025.01.528.42.031.82.530.13.028.4\begin{array}{|c|c|} \hline \text{Mass of zinc added (g)} & \text{Temperature (}^\circ\text{C)} \\ \hline 0.0 & 18.2 \\ \hline 0.5 & 21.6 \\ \hline 1.0 & 25.0 \\ \hline 1.5 & 28.4 \\ \hline 2.0 & 31.8 \\ \hline 2.5 & 30.1 \\ \hline 3.0 & 28.4 \\ \hline \end{array}Mass of zinc added (g)0.00.51.01.52.02.53.0Temperature (∘C)18.221.625.028.431.830.128.4Describe the pattern in temperature change as the mass of zinc added increases from 0.0 g to 3.0 g.
Explain how these results demonstrate that the reaction is exothermic.
State the meaning of the term activation energy by completing the sentence:
"Activation energy is the minimum..."
15 exam-style questions on OCR GCSE Chemistry Energetics. Each one has a worked solution and a mark scheme showing where the marks go.