Which of the following statements about Hydrogen gas is correct?

Concept

The correct answer is option 3, i.e., The H—H bond dissociation enthalpy in hydrogen is the highest for a single bond between two atoms of any element.

• The electrolysis of acidified water using platinum electrodes and traces of acid/ base gives hydrogen gas, but it is not of high purity. Given below is the reaction for the same:
  1. 2H₂O (l) → 2H₂ (g) + O₂ (g)
• High purity (>99.95%) hydrogen gas is obtained by electrolyzing warm aqueous barium hydroxide solution between nickel electrodes. Hence, Option 1 is NOT correct.
• Hydrogen gas is obtained as a by-product in the manufacturing of sodium hydroxide and chlorine by the electrolysis of brine (aq. solution of NaCl) solution. Hence, Option 2 is NOT correct. The reaction for the same is given below:
  • 2Na⁺ (aq) + 2Cl^- (aq) + 2H₂O (l) → Cl₂ (g) + H₂ (g) + 2Na⁺ (aq) + 2OH^- (aq)
• The H—H bond dissociation enthalpy in hydrogen is the highest for a single bond between two atoms of any element. It is because of the following factors:
  • the dissociation of dihydrogen into its atoms is only ~0.081% around 2000 K which increases to 95.5% at 5000 K. 
  • it is relatively inert at room temperature. Hence, Option 3 is correct.
• Presently ~77% of the industrial dihydrogen is produced from petro-chemicals, 18% from coal, 4% from the electrolysis of aqueous solutions, and 1% from other sources. Hence, Option 4 is NOT correct.