Question

$$Me_3CCH_2 COOH$$ is more acidic than $$Me_3SiCH_2COOH$$.

Answer 1

$$Si (E.N. = 1.8)$$ is more electropositive than $$C (E.N. = 2.5)$$, therefore, $$Me_3 Si$$ (trimethylsilyl group) has greater +I-effect than that of $$Me_3C$$ (t-butyl group). As a result, $$Me_3Si$$ intensifies the -ve charge on the carboxylate ion relative to t-butyl group and hence $$Me_3CCH_2COOH$$ is a stronger acid that $$Me_3SiCH_2COOH$$.