Which among the following is benzylic halide?

Which from following is correct regarding $t_{1 / 2}$ of reaction if we double the initial concentration of a reactant in first order reaction?

Identify the product of following reaction.

Formaldehyde + Benzaldehyde $$ \xrightarrow[\mathrm{H}_3 \mathrm{O}^{+}]{\text {conc. } \mathrm{NOH}} \text { product }$$

Which from following is a correct decreasing order of water solubilities of organic compounds?