KO₂(potassium super oxide) is used in oxygen cylinders in space and submarines because it

absorbs CO₂ and increases O₂ content
eliminates moisture
absorbs CO₂
produces ozone

Solution

4KO₂ + 2CO₂ ⟶ 2K₂CO₃ + 3O₂ .KO₂ is used as an oxidising agent. It is used as air purifier in space capsules. Submarines and breathing masks as it produces oxygen and remove carbon dioxide.

The ease of absorption of the hydrated alkali metal ions on an ion-exchange resins follows the order :

Li⁺ < K⁺ < Na⁺ < Rb⁺
Rb⁺ < K⁺ < Na⁺ < Li⁺
K⁺ < Na⁺ < Rb⁺ < Li⁺
Na⁺ < Li⁺ < K⁺ < Rb⁺

Solution

All alkali metal salts are ionic (except Lithium) and soluble in water due to the fact that cations get hydrated by water molecules.The degree of hydration depends upon the size of the cation. Smaller the sizeof a cation, greater is its hydration energy.Relative ionic radii : Cs⁺ > Rb⁺ > K⁺ > Na⁺ > Li⁺
Relative degree of hydration:Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺

Equimolar solutions of the following substances were prepared separately. Which one of these will record the highest pH value ?

BaCl₂
AlCl₃
LiCl
BeCl₂

Solution

(AlCl₃, LiCl & BeCl₂) ) all these solutions are acidic due to cationic hydrolysis, whereas BaCl₂, is salt of strong base and strong acid, hence its solution will almost neutrali.e., pH \(\approx\)7

Solution

Which of the following statements is incorrect?

Pure sodium metal dissolves in liquid ammonia to give blue solution.
NaOH reacts with glass to give sodium silicate
Aluminium reacts with excess NaOH to give Al(OH)₃
NaHCO₃ on heating gives Na₂CO₃

Solution

Which one of the following is present as an active ingredient in bleaching powder for bleaching action ?

CaOCl₂
Ca(OCl)₂
CaO₂Cl
CaCl₂

Solution

Active ingredient in bleaching powder for bleaching action is Ca(OCl)₂

Which of the following compounds has the lowest melting point ?

CaCl₂
CaBr₂
CaI₂
CaF₂

Solution

Melting points of halides decreases as the size of th ehalogen increases. The correct order is CaF₂ > CaCl₂ > CaBr₂ > CaI₂

The compound A on heating gives a colourless gas and a residue that is dissolved in water to obtain B. Excess of CO₂ is bubbled through aqueous solution of B, C is formed which is recovered in the solid form. Solid C on gentle heating gives back A. The compound is

CaSO₄.2H₂O
CaCO₃
Na₂CO₃
K₂CO₃

Solution

Which of the following alkaline earth metal sulphates has hydration enthalpy higher than the lattice enthalpy?

CaSO₄
BeSO₄
BaSO₄
SrSO₄

Solution

Be²⁺ is very small, hence its hydration enthalpy is greater than its lattice enthalpy.

Which of the following oxides is not expected to react with sodium hydroxide?

CaO
SiO₂
BeO
B₂O₃

Solution

NaOH is a strong alkali. It combines with acidic and amphoteric oxides to form salts. Since CaO is a basic oxide hence does not reacts with NaOH.

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