Question

In the industrial production of which of the following, molecular hydrogen is obtained as a byproduct?

• A. NaOH
• B. NaCl
• C. Na metal
• D. \(Na_2CO_3\)

Answer 1

The Correct Option is A

In the industrial production of sodium hydroxide (NaOH), molecular hydrogen (H_2) is obtained as a byproduct. This process is typically carried out using the electrolysis of aqueous sodium chloride (NaCl) solution, known as the Chlor-alkali process.

Let's break down the process step-by-step:

1. Aqueous sodium chloride (NaCl) is subjected to electrolysis. This solution is commonly called brine.
2. During electrolysis, at the anode (positive electrode), chloride ions (Cl^−) are oxidized to produce chlorine gas (Cl_2):
   2Cl^- \rightarrow Cl_2 + 2e^−
3. At the cathode (negative electrode), water molecules are reduced to form hydrogen gas (H_2) and hydroxide ions (OH^−):
   2H_2O + 2e^- \rightarrow H_2 + 2OH^−
4. The overall reaction thus includes the formation of sodium hydroxide (NaOH), along with hydrogen gas and chlorine gas:

Overall reaction:
2NaCl + 2H_2O \rightarrow 2NaOH + H_2 + Cl_2

Therefore, in the industrial production of NaOH (sodium hydroxide), molecular hydrogen (H_2) is indeed obtained as a byproduct.

Conclusion: The correct option is NaOH.