Identify the reactions in which `H_2` is liberated ?
(i)`Zn + NaOH (aq) to `
(ii) ` HCOOH underset(conc.H_2SO_4)overset(373K)(to)`
(iii) ` CH_4 (g) + H_2O (g) underset(Ni)overset(1270 K)(to)`
(iv) `Zn + H^(+) (aq) to `
(v) ` C(s) + H_2O overset(1270 K)(to)`

Options

A. (i), (iii) , (iv) , (v)
B. (i) , (ii) , (iii) , (iv)
C. (ii) , (iii) , (iv) ,(v)
D. (i) , (ii) , (iii) , (v)

Answer

A

Explanation

(i) Zinc is more reactive therefore liberate `H_2` gas in aqueous solution of NaOH
`Zn + 2NaOH(aq) to Na_2ZnO_2 + H_2`
(ii) Formic and liberated CO and `H_2O` on 373 K heating
`HCOOH underset(conc.H_2SO_4)overset(373K)(to) H_2O + CO`
(iii) Methane liberated `H_2` gas on reaction of `H_2O` at 1270 K
`CH_4 (g) + H_2O (g) underset(Ni)overset(1270)(to) CH_2OH + H_2`
(iv) Zn gives `H_2` gas in acidic medium
` Zn + 2H^(+) (aq) to Zn^(2+) + H_2`
(v) Carbon liberate `H_2` gas in aqueous medium at 1270 K
`C + H_2O overset(1270 K)(to) CO + H_2`