In which of the following reactions hydrogen is not liberated?

In which of the following reactions hydrogen is not liberated?
  1. Reaction of fused $\mathrm{NaOH}$ with $\mathrm{C}$
  2. Reaction of $\mathrm{NaOH}$ with sulphur
  3. Heating the concentrated $\mathrm{NaOH}$ with $\mathrm{Si}$
  4. Reaction of zinc with $\mathrm{NaOH}$

Solution

Sodium hydroxide reacts with sulphur to give sodium sulphide and sodium thiosulphate. $4 \mathrm{~S}+6 \mathrm{NaOH} \rightarrow \underset{\substack{\text { sodium } \\ \text { sulphide }}}{2 \mathrm{Na}_2 \mathrm{~S}}+\underset{\substack{\text { sodium } \\ \text { thiosulphate }}}{\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3}+3 \mathrm{H}_2 \mathrm{O}$

Asked in: AP EAMCET 2011

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