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

(1) $CaC{O}_3$                                           

(2) $N{a}_{2}C{O}_3$

(3) $CaS{O}_4.2H_{2}O$                                 

(4) $K_{2}C{O}_3$

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

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

The cation of alkali metals are found as M(H₂O)⁺_n in H₂O, value of 'n' is maximum for

1. Na⁺

2. K⁺

3. Rb⁺

4. Li⁺

1 mole of substance (X) was treated with an excess of water. 2 moles of readily combustible gas were produced along with solution which when reacted with CO₂ gas produced a white turbidity. The substance (X) could be

(1) Ca

(2) CaH₂

(3) Ca(OH)₂

(4) Ca(NO₃)₂

A chloride dissolves appreciably in cold water. When placed on a Pt-wire in Bunsen flame, no distinctive colour is noticed. Cation present is

(1) Mg²⁺

(2) Ba²⁺

(3) Pb²⁺

(4) Ca²⁺

The fire extinguisher contains NaHCO₃ and the compound (X). The compound (X) maybe -

1. CH₃COOH

2. NaOH

3. C₆H₅OH

4. None of the above. 

Alkali metals do not form nitride on reaction with N₂, whereas lithium forms Li₃N, because

(1) High ionisation energy of Li

(2) High lattice energy of Li₃N

(3) High sublimation energy of Li

(4) High covalent nature of Li₃N

All group-2 metals dissolve in liquid ammonia to produce a bright blue colour. The colour is due to-

1. A change in the structure of ammonia.

2. d-d transition.

3. The spectrum of the solvated electrons.

4. An electronic transition from a lower to a higher energy state.

$∆{\mathrm{H}}_{\mathrm{solution}}$ is positive for

I. LiF

II. CsI

III. RbF

IV. KF

(1) I, II, III & IV

(2) II only

(3) I only

(4) I & II only

While moving down the group (in alkaline earth metals) following property increases except

(1) Radius

(2) Solubility of hydroxides

(3) Solubility of sulphates

(4) Thermal stability of carbonates