The reaction of diborane in diethylether with $\underline{X}$ gives metal borohydride. $X$ is a

$H_2SO_4$ acts as a dehydrating agent in its reaction with:

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R).$
Assertion $(A):$ Heavy water is used for the study of reaction mechanism.
Reason $(R):$ The rate of reaction for the cleavage of $O-H$ bond is slower than that of $O-D$ bond.
Choose the most appropriate answer from the options given below:

Which property of hydrogen distinguishes it from alkali metals?

Which of the following is a synthesis gas?

Hydrogen generally forms covalent compounds. Give reason.