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19
MCQ (Single Correct Answer)

In which of the following reactions, the equilibrium remains unaffected on addition of small amount of argon at constant volume?

A
$\mathrm{H}_2(\mathrm{g})+\mathrm{I}_2(\mathrm{g}) \rightleftharpoons 2 \mathrm{HI}(\mathrm{g})$
B
$\mathrm{PCl}_5(\mathrm{g}) \rightleftharpoons \mathrm{PCl}_3(\mathrm{g})+\mathrm{Cl}_2(\mathrm{g})$
C
$\mathrm{N}_2(\mathrm{g})+3 \mathrm{H}_2(\mathrm{g}) \rightleftharpoons 2 \mathrm{NH}_3(\mathrm{g})$
D
The equilibrium will remain unaffected in all the three cases
20
MCQ (Multiple Correct Answer)

For the reaction $\mathrm{N}_2 \mathrm{O}_4(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NO}_2(\mathrm{~g})$, the value of K is 50 at 400 K and 1700 at 500 K . Which of the following option(s) is/are correct?

A
The reaction is endothermic
B
The reaction is exothermic
C
If $\mathrm{NO}_2(g)$ and $\mathrm{N}_2 \mathrm{O}_4(\mathrm{~g})$ are mixed at 400 K at partial pressures 20 bar and 2 bar respectively, more $\mathrm{N}_2 \mathrm{O}_4(\mathrm{~g})$ will be formed
D
The entropy of the system increases
21
MCQ (Multiple Correct Answer)

At a particular temperature and atmospheric pressure, the solid and liquid phases of a pure substance can exist in equilibrium. Which of the following term defines this temperature?

A
Normal melting point
B
Equilibrium temperature
C
Boiling point
D
Freezing point
22
Subjective

The ionisation of hydrochloric acid in water is given below

$$\mathrm{HCl}(\mathrm{aq})+\mathrm{H}_2 \mathrm{O}(l) \rightleftharpoons \mathrm{H}_3 \mathrm{O}^{+}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq})$$

Label two conjugate acid-base pairs in this ionisation.

Explanation

23
Subjective

The aqueous solution of sugar does not conduct electricity. However, when sodium chloride is added to water, it conducts electricity. How will you explain this statement on the basis of ionisation and how is it affected by concentration of sodium chloride?

Explanation

Explanation for the given statement on the basis of ionisation and effect upon the concentration of sodium chloride is given below

(i) Sugar being a non-electrolyte does not ionise in water whereas NaCl ionises completely in water and produces $\mathrm{Na}^{+}$and $\mathrm{Cl}^{-}$ion which help in the conduction of electricity.

(ii) When concentration of NaCl is increased, more $\mathrm{Na}^{+}$ and $\mathrm{Cl}^{-}$ ions will be produced. Hence, conductance or conductivity of the solution increases.