Identify the catalyst $X$ used in the following reaction: $CH_{3}CH_{2}Br + 2[H] \stackrel{X}{\longrightarrow} CH_{3}CH_{3} + HBr$

Identify the major product of the dehydrohalogenation of $CH_3-CH_2-CH(Br)-CH_3$ using an alcoholic base.

Which is the correct decreasing order of boiling points for the following compounds?

The reaction of chloroform with concentrated $HNO_3$ yields ........

The increasing order of the reactivity of the following halides for the $S_N1$ reaction is:
$(I)$ $CH_3-CHCl-CH_2-CH_3$
$(II)$ $CH_3-CH_2-CH_2-Cl$
$(III)$ $p-CH_3O-C_6H_4-CH_2Cl$

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