Science — AI-generated practice question

Common salt (NaCl) is the raw material for several important chemicals:

(i) Sodium Hydroxide:
Electrolysis of brine (aqueous NaCl) — the chlor-alkali process — gives NaOH, Cl₂, and H₂:
$$2\text{NaCl(aq)} + 2\text{H}_2\text{O(l)} \rightarrow 2\text{NaOH(aq)} + \text{Cl}_2\text{(g)} + \text{H}_2\text{(g)}$$

(ii) Bleaching Powder:
Cl₂ obtained above reacts with dry slaked lime:
$$2\text{Ca(OH)}_2 + 2\text{Cl}_2 \rightarrow \text{Ca(ClO)}_2 + \text{CaCl}_2 + 2\text{H}_2\text{O}$$

(iii) Baking Soda (NaHCO₃):
NaCl reacts with water, CO₂, and NH₃:
$$\text{NaCl} + \text{H}_2\text{O} + \text{CO}_2 + \text{NH}_3 \rightarrow \text{NH}_4\text{Cl} + \text{NaHCO}_3$$

(iv) Washing Soda (Na₂CO₃·10H₂O):
Baking soda is heated to give Na₂CO₃, which on recrystallisation gives washing soda:
$$2\text{NaHCO}_3 \xrightarrow{\Delta} \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} + \text{CO}_2$$
$$\text{Na}_2\text{CO}_3 + 10\text{H}_2\text{O} \rightarrow \text{Na}_2\text{CO}_3\cdot10\text{H}_2\text{O}$$

Source: Chapter 2, Section 2.4.3

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• The question is essentially asking you to trace a chain: NaCl → NaOH/Cl₂ → Bleaching powder; NaCl → NaHCO₃ → Na₂CO₃ → Washing soda.
• Examiners expect all four reactions written and balanced — that's where most marks lie.
• Name the process (chlor-alkali) for NaOH — it's a frequently asked term.
• For washing soda, show two steps: heating baking soda first, then recrystallisation. Don't skip either.
• Keep prose minimal; let the equations do the work.