Which alkali metal has the lowest melting point and exists as a liquid –

(1) Na                                                             

(2) K 

(3) Rb                                                             

(4) Cs

Two metals X and Y form covalent halides. Both halides can act as Lewis acids and a catalyst in Friedel Crafts reaction. Halide of X is polymer in the solid state and a dimer in the vapour state which decomposes to monomer at 1200 K. However, halide of Y is a dimer in vapour state and becomes ionic in polar solvent. X and Y are respectively.

(A) Be, Al                                             

(B) Al, Be

(C) Be, Ca                                             

(D) Mg, Ca

Solubility of sulphates in water decreases from $MgS{O}_4$ to $BaS{O}_4$. It is due to the fact that –

(1) Ionic nature increases

(2) Size of $M^{2+}$ ion increases

(3) Lattice energy decrease

(4) Hydration enthalpy of $M^{2+}$ ions decreases

In the Solvay process of manufacturing sodium carbonate, the raw materials used are :

1. Aqueous NaOH, ${\mathrm{NH}}_3$ and ${\mathrm{CO}}_2$

2. Molten NaOH, ${\mathrm{NH}}_3$ and CO

3. Brine NaCl, ${\mathrm{NH}}_3$ and CO

4. Brine NaCl, ${\mathrm{NH}}_3$ and ${\mathrm{CO}}_2$

Blue colour of the solution of alkali metal in ammonia is due to the presence of-

1. $M^{-}$atoms                                         

2. $M^{+}$ ions 

3. Solvated anions                             

4. Solvated electrons

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⁺