A blue coluored solution of an alkali metal in liq NH₃ is due to the presence of -

1. ${\mathrm{M}}^{-}$atoms.                                         

2. ${\mathrm{M}}^{+}$ ions .

3. Solvated anions  .                           

4. Solvated electrons.

Alkali metal ions are- 

1. Diamagnetic and coloured.

2. Diamagnetic and colourless.

3. Paramagnetic and coloured.

4. Paramagnetic and colourless.

A compound X on heating gives a colourless gas. The residue is dissolved in water to obtain Y. Excess $C{O}_2$ is bubbled through an aqueous solution of Y, and Z is formed. Z on gentle heating gives back X. The compound X is-

1. ${\mathrm{CaCO}}_3$                                           

2. ${\mathrm{Na}}_2{\mathrm{CO}}_3$

3. ${\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}$                                 

4. ${\mathrm{K}}_2{\mathrm{CO}}_3$

Magnesia can be prepared by -

1. Burning Mg in air.

2. Heating hydroxide, nitrate, sulphate or carbonate of magnesium.

3. Heating Mg in steam.

4. All of the above.

A compound insoluble in acetic acid is  -

1. Calcium oxide.                    

2. Calcium carbonate.

3. Calcium oxalate.                      

4. Calcium hydroxide.

Assertion :  LiF is almost insoluble in water

Reason :  LiCl is soluble not only in water but also in acetone.

Assertion : s-block elements do not occur free in nature

Reason:  s-block elements are highly electropositive in nature.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true, but R is not the correct explanation of A.

3. A is true, but R is false.

4. Both A and R are false.

Assertion : Potassium and caesium are useful as electrodes in photoelectric cells.

Reason :  Potassium and caesium, when irradiated with light, the light energy absorbed is sufficient to eject out the electron from an atom.

Assertion :  The alkaline earth metals have much higher melting and boiling points than those of the alkali metals.

Reason : The melting and boiling points of alkaline earth metal do not vary in a regular fashion.

Assertion : The ionisation enthalpies of alkaline earth metals are fairly low.

Reason : In general, the low ionisation enthalpies of alkaline earth metals are due to large size of their atoms.