Q14 / 160 · TS EAMCET 2018 (05 May Shift 1) · Chemistry
Identify the reactions in which $\mathrm{H}_2$ is liberated?
(i) $\mathrm{Zn}+\mathrm{NaOH}(a q) \longrightarrow$
(ii) $\mathrm{HCOOH} \xrightarrow[\text { Conc. } \mathrm{H}_2 \mathrm{SO}_4]{373 \mathrm{~K}}$
(iii) $\mathrm{CH}_4(g)+\mathrm{H}_2 \mathrm{O}(g) \xrightarrow[\mathrm{Ni}]{\stackrel{1270 \mathrm{~K}}{\longrightarrow}}$ (iv) $\mathrm{Zn}+\mathrm{H}^{+}(a q) \longrightarrow$
(v) $\mathrm{C}(s)+\mathrm{H}_2 \mathrm{O}(g) \xrightarrow{1270 \mathrm{~K}}$
- Correct answerA(i), (iii), (iv), (v)
- B(i), (ii), (iii), (iv)
- C(ii), (iii), (iv), (v)
- D(i), (ii), (iii), (v)
Solution
(i) Zinc is more reactive therefore liberate $\mathrm{H}_2$ gas in aqueous solution of $\mathrm{NaOH}$.
$$
\mathrm{Zn}+2 \mathrm{NaOH}(\mathrm{aq}) \longrightarrow \mathrm{Na}_2 \mathrm{ZnO}_2+\mathrm{H}_2
$$
(ii) Formic acid liberated $\mathrm{CO}$ and $\mathrm{H}_2 \mathrm{O}$ on $373 \mathrm{~K}$ heating.
$$
\mathrm{HCOOH} \underset{\text { Conc. } \mathrm{H}_2 \mathrm{SO}_4}{\stackrel{373 \mathrm{~K}}{\longrightarrow}} \mathrm{H}_2 \mathrm{O}+\mathrm{CO}
$$
(iii) Methane liberated $\mathrm{H}_2$ gas on reaction of $\mathrm{H}_2 \mathrm{O}$ at $1270 \mathrm{~K}$.
$$
\mathrm{CH}_4(g)+\mathrm{H}_2 \mathrm{O}(g) \xrightarrow[\mathrm{Ni}]{\stackrel{1270 \mathrm{~K}}{\longrightarrow}} \mathrm{CH}_3 \mathrm{OH}+\mathrm{H}_2
$$
(iv) $\mathrm{Zn}$ gives $\mathrm{H}_2$ gas in acidic medium.
$$
\mathrm{Zn}+2 \mathrm{H}^{+}(a q) \longrightarrow \mathrm{Zn}^{2+}+\mathrm{H}_2
$$
(v) Carbon liberate $\mathrm{H}_2$ gas in aqueous medium at $1270 \mathrm{~K}$.
$$
\mathrm{C}+\mathrm{H}_2 \mathrm{O} \xrightarrow{1270 \mathrm{~K}} \mathrm{CO}+\mathrm{H}_2
$$
Hence, the correct answer is option: 'A'.