W is a strong base that liberates ammonia and fully neutralizes acid

Steps:

• Property 1: Excess W reacts with NH4Cl to release NH3 gas, which is basic and turns red litmus blue, indicating W is a base (NH4+ + OH- → NH3 + H2O).
• Property 1 excludes acids, as they do not produce basic gases with NH4Cl.
• Property 2: Excess W shifts pH from 3 (acidic) to 13 (strongly basic), requiring complete dissociation to provide high [OH-].
• Property 2 rules out weak bases, which cannot achieve such high pH due to partial ionization.

Why B is correct:

• Strong bases like NaOH fully ionize (NaOH → Na+ + OH-), supplying enough OH- to produce pH 13 after neutralizing acid.

Why the others are wrong:

• A: Strong acid would lower pH further and not produce basic NH3 gas.
• C: Weak acid cannot generate basic gas or raise pH to 13.
• D: Weak base produces some NH3 but insufficient OH- for pH 13.

Final answer: B