The correct order of acidic character of the following compounds is:

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phosphorus,aliphatic carboxylic acids react with chlorine or bromine to yield a compound in which $\alpha$-hydrogen has been replaced by a halogen.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:

When carboxylic acid reacts with organolithium reagents to give ketones,side reactions sometimes occur. For example,
$HOCH_2CH_2CH(CH_3)CH_2CH_2COOH$ $\xrightarrow[(x) \, CH_3Li]{tetrahydro\,furan}$ $\xrightarrow[NH_4Cl]{H_2O}$ $\underset{63\%}{\text{Compound } A: HOCH_2CH_2CH(CH_3)CH_2CH_2COCH_3}$ + $\underset{37\%}{\text{Compound } (B)}$
The value of $(x)$ in the above reaction is:

The compound that undergoes decarboxylation most readily under mild conditions is:

$2CH_3COOH \xrightarrow{P_2O_5} ........;$ What will be the product of this reaction?

The reagent that can be used to distinguish between methanoic acid and ethanoic acid is