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Hydrogen

Multiple Choice Questions

121.

Assertion : Compressibility factor for hydrogen varies with pressure with positive slope at all pressures.

Reason : Even at low pressures, repulsive forces dominate hydrogen gas.

If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

122.
The reagent commonly used to determine hardness of water titrimetrically is

oxalic acid

disodium salt of EDTA

sodium citrate

sodium thiosulphate

disodium salt of EDTA

The reagent commonly used to determine hardness of water titrimetrically is disodium salt of EDTA. It is used for the estimation of M²⁺ metal ions like Mg²⁺, Ca²⁺ etc by complexometric titrations. In this method, indicator ions (D^3-ions) form red metal indicator complex with M²⁺ ions.

(i) $\underset{({Mg}^{2 +} or {Ca}^{2 +})}{\underset{metal ion}{M^{2 +}}} + \underset{ion (blue)}{\underset{indicator}{D^{3 -}}} \overset{pH = 10}{⇌} \underset{complex (red)}{\underset{Metal indicator}{[M^{2 +} D^{-}]}}$

(ii) $\underset{(red)}{[M^{2 +} D]^{-}} + \underset{EDTA ion}{{EDTA}^{4 -}} ⇌ \underset{metal - EDTA complex}{[M^{2 +} (EDTA)]^{2 -}} + \underset{(blue)}{D^{3 -}}$

The release of the free indicator ion is marked by a change from red (colour of [M²⁺D]^- complex) to blue (colour of D^3- ion) colour.

123.

Assertion : Increasing pressure on pure water decreases its freezing point.

Reason : Density of water is minimum at 273 K.

If both assertion and reason are true and the reason is the correct explanation of the assertion.
If both assertion and reason are true and the reason is not the correct explanation of the assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

124.

Assertion : The micelle formed by sodium stearate in water has - COO^- groups at the surface.

Reason : Surface tension of water is reduced by the addition of stearate.

If both assertion and reason are true and the reason is the correct explanation of the assertion.
If both assertion and reason are true and the reason is not the correct explanation of the assertion.
If assertion is true but reason is false.
If both assertion and reason are false.