The metal X is prepared by the electrolysis of fused chloride.It reacts with hydrogen to form a colourless solid from which hydrogen is released on treatment with water. The metal is :

Solution

Ca + H₂ ⟶ CaH₂ + 2H₂O ⟶ Ca(OH)₂+ 2H₂

On being placed in water, sodium peroxide not only produces an alkaline solution but also some bubbles. If we assume that the peroxide ion picks up two protons from water to produce a compound that can be seen as the dibasic conjugate acid of peroxide ion and then this compound undergoes a redox disproportion.Using the above information complete the following equation.
Na₂O₂(s) + H₂O(l) ⟶ (A) + (B)
(A) and (B) are

H₂O₂ and NaOH
H₂O and O₂
NaOH and O₂
Na₂O and NaOH

Solution

Which of the following sulphates have the highest solubility in water?

MgSO₄
BaSO₄
CaSO₄
BeSO₄

Solution

An aqueous solution of salt ‘R’ when treated with dil HCl, a colourless gas is given out. The gas so evolved when passed through acidified KMnO₄ decolourises KMnO4 solution.The salt ‘R’ is

Na₂CO₃
NaClO₃
NaNO₂
Na₂SO₃

Solution

Since ‘R’ gives a colourless gas on reaction with dil HCl,so it contains \(CO_{3}^{2-}\) or \(SO_{3}^{2-}\) as anion (i.e., CO2 or SO2 is evolved)Since the gas decolourises acidified KMnO₄ solution so it is SO2 and thus the anion present is \(SO_{3}^{2-}\) i.e., the salt ‘R’ is Na₂SO₃.

Based on lattice energy and other considerations which one of the following alkali metal chlorides is expected to have the highest melting point

LiCl
NaCl
KCl
RbCl

Solution

Although lattice energy of LiCl is higher than NaCl but LiCl is covalent in nature and NaCl ionic there after, the melting point decreases as we move towards NaCl because the lattice energy decreases as a size of alkali metal atom increases (lattice energy α melting point of alkali metal halide)

The metals A nd B form oxide but B also forms nitride when both burn in air.The A and B are

Cs, K
Mg, Ca
Li, Na
K, Mg

Solution

On heating anhydrous Na₂CO₃,…….is evolved

CO₂
Water vapour
CO
No gas

Solution

Anhydrous form of Na₂CO₃ does not decompose on heating even to redness. It is a amorphous powder called soda ash.

In curing cement plasters water is sprinkled from time to time. This helps in

developing interlocking needle-like crystals of hydrated silicates
hydrating sand and gravel mixed with cement
converting sand into silicic acid
keeping it cool

Solution

Setting of cement is exothermic process which develops interlocking crystals of hydrated silicates.

A metal M readily forms its sulphate MSO₄ which is water-soluble. It forms its oxide MO which becomes inert on heating.It forms an insoluble hyroxide M(OH)₂ which is soluble in NaOH solution. Then M is

Solution

Sulphate of alkaline earth metal are sparingly soluble or almost not soluble in water whereas BeSO₄ is soluble in water due to high degree of solvation.Be(OH)₂ is insoluble in water but soluble in NaOH.

Among LiI, NaI, KI, the one which is more ionic and more soluble in water is :

KI
NaI
LiI
None of these

Solution

Larger cation (K+) develops less polarisation in anion and thus KI has more ionic nature and more soluble in water.

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