A student investigates the rate of reaction between zinc pieces and dilute sulfuric acid.
The student collects and measures the volume of hydrogen gas produced in an inverted measuring cylinder over water.
Which other piece of laboratory equipment could the student use to measure the volume of hydrogen gas collected?
The table shows the volume of hydrogen gas collected at 20-second intervals:
Time (s)Volume of hydrogen gas (cm3)0020254044605880681007412077140791608018080 \begin{array}{|c|c|} \hline \text{Time (s)} & \text{Volume of hydrogen gas } (\text{cm}^3) \\ \hline 0 & 0 \\ 20 & 25 \\ 40 & 44 \\ 60 & 58 \\ 80 & 68 \\ 100 & 74 \\ 120 & 77 \\ 140 & 79 \\ 160 & 80 \\ 180 & 80 \\ \hline \end{array} Time (s)020406080100120140160180Volume of hydrogen gas (cm3)0254458687477798080State the time at which the reaction stops.
The student observes that some zinc pieces are still visible in the conical flask when the reaction stops. Explain why the reaction has stopped.
Another student reacts dilute hydrochloric acid with calcium carbonate. The student performs two experiments using the same mass of calcium carbonate and the same volume of acid:
Experiment 1Experiment 2Calcium carbonate formlarge chipspowderAcid concentration (mol/dm3)1.02.0Reaction time (s)18015 \begin{array}{|c|c|c|} \hline & \text{Experiment 1} & \text{Experiment 2} \\ \hline \text{Calcium carbonate form} & \text{large chips} & \text{powder} \\ \hline \text{Acid concentration } (\text{mol/dm}^3) & 1.0 & 2.0 \\ \hline \text{Reaction time (s)} & 180 & 15 \\ \hline \end{array} Calcium carbonate formAcid concentration (mol/dm3)Reaction time (s)Experiment 1large chips1.0180Experiment 2powder2.015Describe and explain, using the reacting particle model, the difference in the rate of reaction between the two experiments. Suggest how the experimental design could be improved.