Which of the following fuels has the maximum calorific value per gram?

Among the following,the correct statement is

Why does hydrogen occur in a diatomic form rather than in a monoatomic form under normal conditions?

Identify the correct statements from the following:
$i$. Reaction of hydrogen with fluorine occurs even in dark.
$ii$. Manufacture of ammonia by Haber process is an endothermic reaction.
$iii$. $HF$ is an electron-rich hydride.

Which of the following is a drying agent that reacts with $CO_2$ and removes water vapor?

What do you understand by the term non-stoichiometric hydrides? Do you expect this type of hydrides to be formed by alkali metals? Justify your answer.