Question

Chlorine is manufactured by the electrolysis of fused (molten) sodium chloride. What mass of sodium chloride must be electrolyzed to obtain 200 kg of chlorine?

Answer 1

The reaction of the formation of sodium chloride with sodium and chlorine will be:
$2Na+C{{l}_{2}}\to 2NaCl$
When we reverse this reaction, we see that:
$2NaCl\to 2Na+C{{l}_{2}}$
2 moles of sodium chloride produces 1 mole of chlorine gas.

Complete step-by-step answer: Sodium chloride which is easily available from seawater can be obtained by evaporating the seawater. So, we can get chlorine gas from the sodium chloride by electrolyzing it because sodium chloride is an ionic compound.
The reaction of the formation of sodium chloride with sodium and chlorine will be:
$2Na+C{{l}_{2}}\to 2NaCl$
When we reverse this reaction, we see that:
$2NaCl\to 2Na+C{{l}_{2}}$
2 moles of sodium chloride produces 1 mole of chlorine gas.
We want to find the amount of sodium chloride required that must be electrolyzed to get 200 kg of chlorine.
$\underset{x\text{ kg}}{\mathop 2NaCl}\,\to 2Na+\underset{200\text{ kg}}{\mathop C{{l}_{2}}}\,$
The molecular mass of sodium chloride (NaCl) will be = 23 + 35.5 = 58.5. So, for two moles of sodium chloride, the mass will be 117 grams.
The molecular mass of chlorine gas ($C{{l}_{2}}$) will be = 35.5 + 35.5 = 71.
So, we can say that 117 grams of sodium chloride will produce 71 grams of chlorine.
Therefore, 1 gram of sodium chloride will produce = $\frac{71}{117}$ grams of chlorine.
For x kg of NaCl will produce = $\frac{71}{117}\text{ x }x\text{ x 1000 g}$ of chlorine gas.
We need 200 kg of chlorine gas. We can write:
$\frac{71}{117}\text{ x }x\text{ x 1000 = 200 x 1000}$
$x=\frac{200\text{ x 117}}{71}=329.57\text{ kg}$
The amount of sodium chloride required will be 329.57 kg.

Note: When you write the equation, the equation must be balanced so that the number of moles can be written correctly. If you take the mass of sodium chloride as 58.5, then your answer will be wrong.