Which one of the following properties is generally not applicable to ionic hydrides?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Physical properties of isotopes of hydrogen are different.
Reason $R$: Mass difference between isotopes of hydrogen is very large.
In the light of the above statements,choose the correct answer from the options given below:

The calorific value of producer gas is low because of:

Identify the correct statement from the following.

The property of hydrogen which distinguishes it from other alkali metals is

When steam is passed over red hot iron,the substances formed are