A) State Faraday's first law of electrolysis. b) Calculate the volume of chlorine gas liberated at s.t.p. when a current of 100 A is passed for 2 hours through molten sodium chloride.

The current ($I$) is $100 \text{ A}$.
The time ($t$) is $2 \text{ hours}$.
Convert time to seconds:

$$t = 2 \text{ hours} \times 60 \frac{\text{minutes}}{\text{hour}} \times 60 \frac{\text{seconds}}{\text{minute}} = 7200 \text{ s}$$

Calculate charge:

$$Q = I \times t = 100 \text{ A} \times 7200 \text{ s} = 720000 \text{ C}$$

The Faraday constant ($F$) is $96500 \text{ C/mol}$.

$$\text{Moles of electrons} = \frac{Q}{F} = \frac{720000 \text{ C}}{96500 \text{ C/mol}} \approx 7.46114 \text{ mol}$$

In molten sodium chloride, chlorine gas is liberated at the anode:

$$2\text{Cl}^-(l) \to \text{Cl}_2(g) + 2\text{e}^-$$

From the reaction, 2 moles of electrons produce 1 mole of $\text{Cl}_2$.

$$\text{Moles of } \text{Cl}_2 = \frac{\text{Moles of electrons}}{2} = \frac{7.46114 \text{ mol}}{2} \approx 3.73057 \text{ mol}$$

The molar gas volume ($\text{MGV}$) at s.t.p. is $22.4 \text{ dm}^3/\text{mol}$.

$$\text{Volume of } \text{Cl}_2 = \text{Moles of } \text{Cl}_2 \times \text{MGV} = 3.73057 \text{ mol} \times 22.4 \frac{\text{dm}^3}{\text{mol}} \approx 83.565 \text{ dm}^3$$

The volume of chlorine gas liberated at s.t.p. is $\boxed{\text{83.57 dm}^3}$.

9. c) Three applications of electrolysis are:

• Electroplating, such as coating a metal object with a layer of another metal (e.g., silver plating).
• Extraction of reactive metals from their ores, such as aluminium from bauxite.
• Purification of metals, such as refining crude copper.

10. a) Solubility in Chemistry is defined as the maximum mass of a solute that can dissolve in a given mass of solvent (usually $100 \text{ g}$) at a specific temperature to form a saturated solution.

11. b) The table shows the solubility of potassium chlorate (V) at different temperatures: | Mass of $\text{KClO}_3$ in grams per $100\text{g}$ of water | 40.0 | 20.0 | 13.3 | 10.0 | 8.0 | |---|---|---|---|---|---| | Temperature ($^\circ\text{C}$) | 88.0 | 52.0 | 38.0 | 31.0 | 25.0 |