At a particular temperature and atmospheric pressure, the solid and liquid phases of a pure substance can exist in equilibrium. Choose the terms which define this temperature:

(a) Normal melting point

(b) Equilibrium temperature

(c) Boiling point

(d) Freezing point

Choose the correct option:

Match the following equilibria with the corresponding condition.

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PCl₅, PCl₃, and Cl₂ are at equilibrium at 500 K in a closed container and their concentrations are 0.8×10^–3 mol L^–1 , 1.2×10^–3 mol L^–1 and 1.2×10^–3 mol L^–1, respectively.
The value of  K_c  for the reaction PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) will be:
1. 1.8 × 10³ mol L^–1
2. 1.8 × 10³
3. 1.8 × 10^–3 mol L^–1
4. 0.55 × 10⁴

At 500 K, equilibrium constant, K_c, for the following reaction is 5.

$\frac{1}{2}{\mathrm{H}}_2\left(\mathrm{g}\right)+\frac{1}{2}{\mathrm{I}}_2\left(\mathrm{g}\right)\rightleftharpoons \mathrm{HI}\left(\mathrm{g}\right)$

What would be the equilibrium constant K_c for the reaction?

$2\mathrm{HI}\left(\mathrm{g}\right)\rightleftharpoons {\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{I}}_2\left(\mathrm{g}\right)$

1.  0.04

2.  0.4

3.  25

4.  2.5

One mole of H₂O and one mole of CO are taken in a 10 L vessel and heated to 725 K. At equilibrium, 40% of water(by mass) reacts with CO according to the equation,

H₂O _(g) + CO _(g)  $\leftrightharpoons$H_2 (g) + CO_2 (g)

The equilibrium constant for the above-mentioned reaction would be:

A sample of pure PCl₅ was introduced into an evacuated vessel at 473 K.
After equilibrium was attained, a concentration of PCl₅ 
was found to be 0.5 × 10^–1 mol L^–1. If the value of
 K_c is 8.3 × 10^–3 mol L^–1, the concentrations of
PCl₃ and Cl₂ at equilibrium would be:

PCl_5 (g)  $\leftrightharpoons$PCl_3 (g) + Cl_2(g)
 

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