$A$ compound $(a)$,$C_8H_9Br$,gives a white precipitate when heated with alcoholic $AgNO_3$. Oxidation of $(a)$ gives an acid $(b)$. The acid $(b)$,$C_8H_6O_4$,easily forms an anhydride on heating. Identify the compound $(a)$.

Why is it necessary to avoid even traces of moisture during the use of a Grignard reagent?

Two bottles containing $C_6H_5I$ and $C_6H_5CH_2I$ have lost their original labels. They are labeled as $A$ and $B$ for testing. $A$ and $B$ are taken separately in test tubes and boiled with $NaOH$ solution. The final solution of each test tube is acidified with dilute $HNO_3$ and a little $AgNO_3$ is added. Solution $B$ gives a yellow precipitate. Which of the following statements is correct?

What happens when $CCl_4$ is treated with $AgNO_3$?

$1$-chlorobutane on reaction with alcoholic potash gives

Ethylene dichloride $(ClCH_2-CH_2Cl)$ and ethylidene chloride $(CH_3-CHCl_2)$ are isomeric compounds. Identify the statement which is not applicable to both of them.