A student investigated the electrolysis of different substances - AQA - GCSE Chemistry - Question 6 - 2018 - Paper 1

Graphite conducts electricity due to its structure and bonding. Each carbon atom forms three covalent bonds in a planar structure, while one electron per carbon atom is delocalized and moves freely through the structure. These delocalized electrons carry charge, enabling the conduction of electricity through graphite.

The apparatus should be changed from using test tubes to using measuring cylinders. Test tubes cannot accurately measure the volume of gases collected during the experiment, as they do not have proper graduations or a scale.

The results indicate that the volume of hydrogen collected is directly proportional to the time, with a steady increase observed. Initially, up to 8 minutes, chlorine is collected at an increasing rate, but after 8 minutes, its rate becomes constant, matching the volume of hydrogen collected, which remains at a steady rate of 0.45 cm³/min.

One reason for the difference in volume of each gas could be that chlorine reacts with water, or it dissolves in the solution, causing less chlorine gas to be collected compared to hydrogen.

From Figure 8, the volume of chlorine collected after 20 minutes is 6.6 cm³. To convert this to liters, we divide by 1000, giving us 0.0066 dm³. Using the molar volume (24.0 dm³), we calculate the moles of chlorine:

$ext{moles} = \frac{0.0066}{24.0} = 2.75 \times 10^{-4} \text{ mol}$

Thus, the amount in standard form is 2.75 x 10^-4 mol.