Which of the following is the most acidic substance?

Which among the following compounds has the highest boiling point?

In the presence of a small amount of phosphorus,aliphatic carboxylic acids react with chlorine or bromine to yield a compound in which $\alpha$-hydrogen has been replaced by a halogen. This reaction is known as:

Give the reaction for heating benzoic acid with soda lime,also known as the decarboxylation of benzoic acid.

Select the final product from this sequence of reactions.
Acetoacetic ester $\xrightarrow{NaOEt}$ $\xrightarrow{CH_3I}$ $\xrightarrow{NaOEt}$ $\xrightarrow{CH_3CH_2CH_2Br}$

Which of the following is most stable?