Identify the catalyst $(A)$ used in the following reaction:
$CO + H_2O \rightleftharpoons CO_2 + H_2$

Identify the correct statements from the following.
$(i)$ $Zn$ reacts with dilute $HCl$ and aqueous $NaOH$ solution separately and liberates hydrogen.
$(ii)$ $Ti$ and $Zr$ form interstitial hydrides.
$(iii)$ The viscosity of $H_2 O$ is more than the viscosity of $D_2 O$.

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

Calorific value of producer gas is low because of

Given below are two statements :
Statement-$I$: The process of producing syn-gas is called gasification of coal.
Statement-$II$: The composition of syn-gas is $CO + H_2$ ($1 : 1$ ratio).
In the light of the above statements,choose the most appropriate answer from the options given below:

$H_2S$ reacts with $O_2$ to form: