A solid compound 'X' on heating gives CO₂ gas and a residue. The residue mixed with water forms 'Y'. On passing an excess of CO₂ through 'Y' in water, a clear solution, 'Z' is obtained. On boiling 'Z', compound 'X' is reformed. The compound 'X' is:

1. ${\mathrm{CaCO}}_3$

2. ${\mathrm{Na}}_2{\mathrm{CO}}_3$

3. ${\mathrm{K}}_2{\mathrm{CO}}_3$

4. $\mathrm{Ca}{\left({\mathrm{HCO}}_3\right)}_2$

The most convenient method to protect the bottom of the ship made of iron is:

1. Coating it with Red lead oxide.
2. White tin plating.
3. Connect it with the Mg block.
4. Connect it with the Pb block.

Alkali metals are not found in nature in their elemental state because they are : 

1. Less reactive due to low ionization energies.

2. Highly reactive due to low ionization energies.

3. Highly reactive due to low electron gain enthalpy.

4. Less reactive due to low electron gain enthalpy.

The oxidation state of sodium in Na₂O₂ is -

1. +1

2. -1

3. 0

4. +2

Alkali and alkaline earth metals cannot be obtained by chemical reduction method because they are the strongest :

1. Oxidizing agents.

2. Reducing agents.

3. Hydrating agents.

4. Drying agents.

Beryllium and Magnesium do not impart color in flame test, because -

1. Be and Mg have high Ionization Energy.

2. Be and Mg have low Ionization Energy.

3. Be and Mg radiate energy in the Infra-Red region.

4. Be and Mg have a high radius.

The incorrect equation for Solvay process is -

1. $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2+2{\mathrm{NH}}_4\mathrm{Cl}\to {\mathrm{NH}}_3+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{CaCl}}_2$

2. $2{\mathrm{NaHCO}}_3\to {\mathrm{Na}}_2{\mathrm{CO}}_3+{\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}$

3. $2\mathrm{NaCl}+{\mathrm{CaCO}}_3\to {\mathrm{Na}}_2{\mathrm{CO}}_3+{\mathrm{CaCl}}_2$

4. None of the above.

Potassium carbonate cannot be prepared by the Solvay process because -

The hydroxides and carbonates of sodium and potassium are easily soluble in water while the corresponding salts of magnesium and calcium are sparingly soluble in water because -

1. Lattice energies of carbonates and hydroxides formed by calcium and magnesium are much more than those of sodium and potassium.

2. Lattice energies of carbonates and hydroxides formed by sodium and potassium are much more than those of calcium and magnesium.

3. Enthalpy of carbonates and hydroxides formed by calcium and magnesium are much more than those of sodium and potassium.

4. Enthalpy of carbonates and hydroxides formed by sodium and potassium are much more than those of calcium and magnesium.

Lithium salts are generally hydrated because they have :

1. High polarizing power.

2. High ionization enthalpy.

3. High electronegativity.

4. Low polarizing power.