NEET levelSingle correct optionDifficulty 1 of 3g2010
In aqueous solution the pKa values of the conjugate acids are 4.6 for the anilinium ion (CX6HX5NHX3X+) and 10.6 for the methylammonium ion (CHX3NHX3X+). Which statement is correct?
Athe anilinium ion is the stronger acid, so aniline is a stronger base than methylamine
Bthe methylammonium ion is the stronger acid, so methylamine is a weaker base than aniline
Cthe anilinium ion is the stronger acid, so aniline is a weaker base than methylamine
Dboth ions have the same acidity, so the two amines have equal basicity
Answer: C
A lower pKa means a stronger acid. Anilinium (4.6) is a stronger acid than methylammonium (10.6). The stronger the conjugate acid, the weaker the parent base, so aniline is a weaker base than methylamine.