## Class 11 - Chemistry

#### Equilibrium

MCQ
Q&A
Question:

A sparingly soluble salt gets precipitated only when the product of concentration of its ions in the solution (Qsp) becomes greater than its solubility product. If the solubility of BaS04 in water is 8 x 10-4 mol dm-3, calculate its solubility in 0.01 mol dm-3 of H2S04.

Equilibrium - Questions
1.

At 1127 K and 1 atmosphere pressure, a gaseous mixture of CO and C02 in equilibrium with solid carbon has 90.55% CO by mass.

Calculate Kc for the reaction at the above temperature.

2.

Calculate (a) âˆ†G and (b) the equilibrium constant for the formation of N02 from NO and 02 at 298 K

3.

Hydrogen gas is obtained from the natural gas by partial oxidation with steam as per following endothermic reaction:

Write the expression for Kpfor the above reaction
How will the value of Kp and composition of equilibrium mixture be affected by:
(i) increasing the pressure, (ii) increasing the temperature, (iii) using a catalyst?

4.

What is the effect of:
(iii) removal of CO (iv) removal of  CH3OH

5.

At 473 K, the equilibrium constant Kc for the decomposition of phosphorus pentachloride (PCl5) is 8.3 x 10-3 . if decomposition proceeds as:

(a) Write an expression for Kc for the reaction
(b) What is the value of Kc for the reverse reaction at the same temperature.
(c) What would be the effect on Kc if
(i) More of PCl5is added (ii) Temperature is increased.

6.

Dihydrogen gas used in Haber’s process is produced by reacting methane from natural gas with high temperature steam. The first stage of two stage reaction involves the formation of CO and H2 In second stage, CO formed in first stage is reacted with more steam in water gas shift reaction.

If a reaction vessel at 400 °C is charged with an equimolar mixture of CO and steam so that  PCO  = PH2O = 4.0 bar, what will be the partial pressure of H2 at equilibrium? Kp = 0.1 at 400 °C.

7.

Predict which of the following will have appreciable concentration of reactants and products:

8.

The value of Kc for the reaction  302(g) —>203(g) is 2.0 x 10-50  at 25 °C. If equilibrium concentration of 02 in air at 25 °C is 1.6 x 10-2, what is the concentration of O3?

10.

What is meant by conjugate acid-base pair? Find the conjugate acid/base for the following species:  HNO2, CH, HClO4 , OH, CO32-, S2-

11.

Which of the following are Lewis Acids?
H2O,BF3, H+ and NH4+,

12.

What will be the conjugate bases for the Bronsted acids?HF, H2S04 and H2C03?

13.

Write the conjugate acids for the following Bronsted bases:
NH2, NH3 and HCOO

14.

The species  H20, HCO3, HSO4 and NH3  can act both as Bronsted acid and base. For each case, give the corresponding conjugate acid and base.

15.

Classify the following species into Lewis acids and Lewis bases and show how these can act as Lewis acid/Lewis base?
(a) OHions (b) F(c) H+ (d) BCl3

16.

The concentration of hydrogen ions in a sample of soft drink is 3.8 x  10-3  M. What is the pH value?

17.

The pH of a sample of vinegar is 3.76. Calculate the concentration of hydrogen ion in it.

18.

The ionization constant of HF, HCOOH and HCN at 298 K are is 6.8 x 10-4 , 1.8 x 10-4 and 4.8 x 10-9  respectively, Calculate the ionization constant of the corresponding conjugate base.

19.

The ionization constant of phenol is 1.0 x 10-10. What is the concentration of phenolate ion in 0.05 M solution of phenol? What will be its degree of ionization if the solution is also 0.01 M in sodium phenolate?

20.

The-first ionization constant of H2S is 9.1 x  10-8. Calculate the concentration of HS ions in its 0.1 M solution and how will this concentration be affected if the solution is 0.1 M in HCl also? If the second dissociation constant of H2S is 1.2 x 10-13, calculate the concentration of S2-under both conditions.

21.

The ionization constant of acetic acid is 1.74 x  10-5. Calculate the degree of dissociation of acetic acid in its 0.05 M solution. Calculate the concentration of acetate ions in the solution and its pH.

22.

It has been found that the pH of a 0.01 M solution of an organic acid is 4.15. Calculate the concentration of the anion, the ionization constant of the acid and its  PKa.

23.

Assuming complete dissociation, calculate the pH of the following solutions:
(a) 0.003 M HCl (b) 0.005 M NaOH (c) 0.002 M HBr  (d) 0.002 M KOH

24.

Calculate the pH of the following solutions:
(a) 2g ofTlOH dissolved in water to give 2 litre of the solution
(b) 0.3 g of  Ca(OH)2  dissolved in water to give 500 mL of the solution
(c) 0.3 g of NaOH dissolved in water to give 200 mL of the solution
(d) l mL of 13.6 M HCl is diluted with water to give 1 litre of the solution.

25.

The degree of ionization of a 0.1 M bromoacetic acid solution is 0.132. Calculate the pH of the solution and the PKa  of bromoacetic acid.

26.

The pH of0.005 M codeine (C18H21N03) solution is 9.95. Calculate the ionization constant and  PKb.

27.

What is meant by equilibrium ?

28.

What is meant by reaction quotient?

29.

What is meant by ionic product of water (kw)?

30.

Define solubility product.

31.

How does common ion affect the solubility of electrolyte?

32.

Write conjugate add and conjugate base of H2O?

33.

Give two characteristics of a buffer solution.

34.

How does a catalyst affect the equilibrium constant?

35.

What is basic buffer?

36.

S032-is Bronsted base or acid and why?

37.

What is the relationship between Kp and  Kc  ?

38.

Define common ion effect.

39.

Write the equilibrium constant (Kc) expression for the following reactions.

40.

In the reaction A + B———> C + D, what will happen to the equilibrium if concentration of A is increased?
(b) The equilibrium constant for a reaction is 2 x 10-23    at 25 °C and 2 x 10-2 at 50 °C. Is the reaction endothermic or exothermic?
(c) Mention at least three ways by which the concentration of S03 can be increased in the following reaction in a state of equilibrium.

41.

(i) Define Le Chatelier’s principle.
(ii) Following reactions occur in a Blast furnace.
Fe203(s) + 3CO(g) ———–>2Fe(s) + 3CO2(g)
use Le chatelier’s principle to predict the direction of reaction when equilibrium mixture is disturbed by
(a) adding Fe203 (b) removing CO2 .
(c) removing CO.

42.

(i) Point out the differences between ionic product and solubility product.
(ii) The solubility of AgCl in water at 298 K is 1.06 x 10-5  mole per litre. Calculate its solubility product at this temperature.

43.

At certain temperature and under a pressure of 4 atm, PCl5 is 10% dissociated.  Calculate the pressure at which PCl5 will be 20% dissociated at temperature remaining constant.

44.

For the equilibrium 2 NOCl(g)——-> 2NO(g) + Cl2(g) the value of the equilibrium constant Kc is 3.75 x 10-6 at 1069 K. Calculate the Kp  for the reaction at this temperature?

45.

The values of Ksp of two sparingly soluble salts  Ni(OH)2  and AgCN are 2.0 x 10-15    and 6 x 10-17    respectively. Which salt is more soluble? Explain.

46.

The value of Kc for the reaction 2A——>B + C is 2 x 10-3. At a given time, the composition of reaction mixture is [A] = [B] = [C] = 3 x 10-4 M. In which direction the reaction will proceed?

47.

PCl5, PCl3 and Cl2 are at equilibrium at 500 K and having concentration 1.59M PCl5 1.59M Cl2 and 1.41M PCl5. Calculate Kc for the reaction PCl5———>PC13+ Cl2

48.

Dihydrogen gas is obtained from natural gas by partial oxidation with steam as per following endothermic reaction:
CH4(g) + H2O(g) ——> CO(g) + 3 H2(g)
(a) Write an expression for Kpfor the above reaction.
(b) How will the values of Kp and composition of equilibrium mixture be affected by (i) increasing the pressure (ii) increasing the temperature (iii) using a catalyst?

49.

The ionization constant of an acid, Ka is the measure of strength of an acid. The Ka values of acetic acid, hypochlorous acid and formic acid are 1.74 x 10-5, 3.0 x 10-8 and 1.8 x 10-4 Which of the following orders of pH of 0.1 mol dm-3 solutions of these acids is correct?
(a) acetic acid > hypochlorous acid > formic acid
(b) hypochlorous acid > acetic acid > formic acid
(c) formic acid > hypochlorous acid > acetic acid
(d) formic acid > acetic acid > hypochlorous acid

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