Chemistry Class 11 NCERT Solutions: Chapter 7: Equilibrium Part 7 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q: 19. A sample of pure was introduced into an evacuated vessel at 473 K. After equilibrium was attained, concentration of was found to be . If value of is , what are the concentrations of at equilibrium?

Phosphorus Pentachloride


Let the concentration of both . The given reaction is:

It is given that the value of equilibrium constant, .

Now we can write the expression for equilibrium as:


Therefore, at equilibrium,


Q: 20. One of the reactions that takes place in producing steel from iron ore is the reduction of iron (II) oxide by carbon monoxide to give iron metal and

What is the equilibrium partial pressures of and at 1050 K if the initial partial?

Pressures are:


For the given reaction,

It is given that

Since , the reaction will proceed in the backward direction.

Therefore, we can say that the pressure of CO will increase while the pressure of will decrease

Now, let the increases in pressure of in pressure of be p. Then we can write,

Therefore, equilibrium partial of

And, equilibrium partial pressure of

Q: 21. Equilibrium constant, for the reaction

at 500 K is 0.061.

At a particular time, the analysis shows that composition of the reaction mixture is . Is the reaction at equilibrium? If not in which direction does the reaction tend to proceed to reach equilibrium?


The given reaction is:

Now, we know that,

It is given that .

Since the reaction is not at equilibrium.

Since , the reaction will proceed in the forward direction to reach equilibrium.

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