Acid-base reaction producing ammonia gas

Steps:

• NaOH(aq) reacts with NH4Cl(aq) upon warming to produce NH3 gas and NaCl(aq).
• NH3 gas turns damp litmus paper blue, confirming it as a base.
• In Brønsted-Lowry theory, the reaction is NH4+(aq) + OH-(aq) → NH3(aq) + H2O(l).
• NH4+ donates H+ (acid), while OH- accepts H+ (base), so NaOH acts as base, NH4Cl as acid source.

Why B is correct:

• B matches NaOH as Brønsted-Lowry base (OH- accepts proton) and NH4Cl as acid (NH4+ donates proton), per the reaction formula.

Why the others are wrong:

• A reverses roles, ignoring NH4+ as proton donor.
• C mislabels NaOH, which is not a proton donor.
• D mislabels NH4Cl, which provides proton donor NH4+.

Final answer: B