Very pure hydrogen $(99.9 \%)$ can be made by which of the following processes?

The correct statements among $(a)$ to $(d)$ regarding $H_2$ as a fuel are:
$(a)$ It produces fewer pollutants than petrol.
$(b)$ $A$ cylinder of compressed dihydrogen weighs $\sim 30$ times more than a petrol tank producing the same amount of energy.
$(c)$ Dihydrogen is stored in tanks of metal alloys like $NaNi_5$.
$(d)$ On combustion,the values of energy released per gram of liquid dihydrogen and $LPG$ are $142$ and $50 \ kJ,$ respectively.

One would expect a proton to have a very large:

Saline hydrides are known to react with water violently producing fire. Can $CO_2$,a well-known fire extinguisher,be used in this case? Explain.

The correct order of boiling point of $H_2$,$HD$,$D_2$ and $T_2$ would be

Calorific value of producer gas is low because of