Chemistry 5070/31 — May/June 2020

Use the apparatus shown with the boiling tube in a rack and the measuring cylinder supported with a stand and clamp.

Fill the trough and measuring cylinder with water.

• Remove the bung from the boiling tube.
• Place one strip of Q into the boiling tube.
• In experiment 1 add $4.0\text{ cm}^3$ of water and then $6.0\text{ cm}^3$ of P to the boiling tube.
• Quickly insert the bung back into the boiling tube.
• Immediately start timing.
• Stop timing when $18\text{ cm}^3$ of hydrogen has been collected. Record the time taken to the nearest second in the table.
• Repeat the experiment four more times using the volumes of P and water shown in the table.

P is $2.0\text{ mol/dm}^3$ hydrochloric acid.

Calculate the concentration of hydrochloric acid in each experiment.

Write your answers in the table.

Use data from the table to plot a graph of the concentration of hydrochloric acid ($x$-axis) against the time taken to collect $18\text{ cm}^3$ of hydrogen ($y$-axis).

Draw a curve of best fit.

Calculate the number of moles of hydrogen, $\text{H}_2$, in $18\text{ cm}^3$ of hydrogen at room temperature and pressure (r.t.p.).

[The volume of one mole of hydrogen is $24000\text{ cm}^3$ at r.t.p.]

number of moles of hydrogen = ______

Use your answer from (d) to calculate the number of moles of $\text{HCl}$ that react to form $18\text{ cm}^3$ of $\text{H}_2$ at r.t.p.

$$\text{Mg(s)} + 2\text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)}$$

number of moles of $\text{HCl}$ = ______

Use data from the table and your answer from (e) to calculate the mean rate of reaction, in $\text{mol/s}$, of P in experiment 5.

Give your answer to two significant figures.

mean rate of reaction in experiment 5 = ______ $\text{mol/s}$