Metallic hydrides are useful for hydrogen storage because : 

1. Metallic hydrides are oxygen-rich.

2. Metallic hydrides are oxygen-deficient.

3. Metallic hydrides are hydrogen-rich.

4. Metallic hydrides are hydrogen-deficient.

Atomic hydrogen or oxy-hydrogen torch is used for cutting and welding purposes because:

 The correct order of hydrogen bonding among ${\mathrm{NH}}_3$, H2O and HF, is 

1. HF > ${\mathrm{H}}_2\mathrm{O}$ > ${\mathrm{NH}}_3$

2. ${\mathrm{H}}_2\mathrm{O}$ > HF > ${\mathrm{NH}}_3$

3. HF > ${\mathrm{NH}}_3$ > ${\mathrm{H}}_2\mathrm{O}$

4. ${\mathrm{NH}}_3$ > HF > ${\mathrm{H}}_2\mathrm{O}$

CO2  is used as a fire extinguisher because -

1. ${\mathrm{CO}}_2$ has high lattice energy.

2. ${\mathrm{CO}}_2$ will be effective in isolating the burning surface from dihydrogen and dioxygen.

3. ${\mathrm{CO}}_2$ is lighter than dioxygen.

4. ${\mathrm{CO}}_2$ is lighter than dihydrogen.

The term ’auto-protolysis’ of water means :

The correct statement about the reaction of water with fluorine is:

The structure of the common form of ice is :

The temporary and permanent hardness of water is caused by -
1. Permanent hardness is caused by hydrogen carbonates and temporary hardness is caused by chlorides.
2. Temporary hardness is caused by dihydrogen and permanent hardness is caused by oxides.
3. Temporary hardness is caused by insoluble hydrogen carbonates and permanent hardness is caused by chlorides.
4. Temporary hardness is caused by hydrogen carbonates and permanent hardness is caused by chlorides.

The softening of hard water by synthetic ion-exchange resins is based on -

1. Increasing the lattice energy.

2. Physical separation.

3. Lowering the activation energy.

4. Exchange of cations and anions.

Water acts as a base in -

1. Reaction with ${\mathrm{H}}_2\mathrm{S}$

2. Reaction with ${\mathrm{NH}}_3$

3. Reaction with NaOH

4. All of the above