Which of the following is more acidic than phenol?

Arrange these carboxylic acids in decreasing order of ease of esterification with $CH_3OH/H^{+}$:
$(I)$ $CH_3-CH(CH_3)-COOH$
$(II)$ $CH_3-CH(CH_3)-CH_2-COOH$
$(III)$ $CH_3-C(CH_3)_2-COOH$
$(IV)$ $(CH_3-CH_2)_3C-COOH$

Which of the following compounds reacts with methyl magnesium iodide to produce ethyl acetate?

Aspirin is an acetylation product of

Explain decarboxylation with examples. Or,provide the product obtained from the carboxylic acid method with examples.

For which carboxylic acid,the $pK_a$ is the lowest :