#### 12th Standard Chemistry English Medium Ionic Equillibrium Reduced Syllabus Important Questions With Answer Key 2021

12th Standard

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 100

Multiple Choice Questions

15 x 1 = 15
1. Concentration of the Ag+ ions in a saturated solution of Ag2C2O4 is 2.24 ×10-4mol L-1 solubility product of Ag2C2O4 is

(a)

2.42 ×10-8mol3L-3

(b)

2.66 ×10-12mol3L-3

(c)

4.5 ×10-11mol3L-3

(d)

5.619 ×10-12mol3L-3

2. pH of a saturated solution of Ca(OH)2 is 9. The Solubility product ( Ksp) of Ca(OH)2

(a)

0.5 ×10-15

(b)

0.25 ×10-10

(c)

0.125 ×10-15

(d)

0.5 ×10-10

3. Which will make basic buffer?

(a)

50 mL of 0.1M NaOH+25mL of 0.1M CH3 COOH

(b)

100 mL of 0.1M CH3COOH+100 mL of 0.1M NH4OH

(c)

100 mL of 0.1M HCl+200 mL of 0.1M NH4OH

(d)

100 mL of 0.1M HCl+100 mL of 0.1M NaOH

4. What is the decreasing order of strength of bases
OH, NH2- H - C ≡ C and CH3 - CH2-

(a)

OH->NH2- >H-C≡C >CH3-CH2-

(b)

NH2->OH->CH3-CH2- >H-C≡C

(c)

CH3-CH2->NH2->H-C≡C->OH-

(d)

OH->H-C ≡ C->CH3-CH2- >NH2-

5. If the solubility product of lead iodide is 3.2 ×10-8 , its solubility will be

(a)

2×10-3M

(b)

4×10-4M

(c)

1.6 ×10-5M

(d)

1.8 ×10-5M

6. The pH of 10-5M KOH solution will be

(a)

9

(b)

5

(c)

19

(d)

none of these

7. Dissociation constant of NH4OH is 1.8 x 10-5  the hydrolysis constant of NH4Cl would be

(a)

1.8 ×10-19

(b)

5.55 ×10-10

(c)

5.55 ×10-5

(d)

1.80 ×10-5

8. Pick out the incorrect statement regarding Lewis acids and bases

(a)

A Lewis acid is a electron deficient molecule

(b)

Lewis bases is one which donates an electron pair

(c)

Lewis base is a cation

(d)

Lewis acid is a electron deficient molecule and Lewis base is a cation

9. The conjugate base of NH-2 is

(a)

NH-

(b)

NH3

(c)

NH+3

(d)

NH2-

10. The pH of pure water at 25°C is

(a)

0

(b)

1

(c)

7

(d)

14

11. The buffer present in human blood is

(a)

CH3COOH + CH3COONa

(b)

NH4OH + NH4CI

(c)

H2CO3 + H${ CO }_{ 3 }^{ - }$

(d)

CH3COOH + CH3COONa and NH4OH + NH4CI

12. NH4OH is a weak base because

(a)

it has low vapour pressure

(b)

it is only partially ionised

(c)

it is completely ionised

(d)

it has low densit

13. When pH of a solution is 2, the hydrogen ion concentration in moles litre-1 is

(a)

1 x 10-12

(b)

1 x 10-2

(c)

1 x 10-7

(d)

1 x 10-4

14. The Lewis base among the following is ______

(a)

BF3

(b)

NH3

(c)

AICl3

(d)

NH+4

15. The solution whose pH is maintained constant even upon the addition of small amounts of acid or base is called ________

(a)

acidic solution

(b)

basic solution

(c)

buffer solution

(d)

true solution

1. 2 Marks

10 x 2 = 20
16. What are lewis acids and bases? Give two example for each.

17. When aqueous ammonia is added to CuSO4 solution, the solution turns deep blue due to the formation of tetramminecopper (II) complex,${ [Cu({ H }_{ 2 }O)] }_{ (aq) }^{ 2+ }\rightleftharpoons 4{ NH }_{ 3 }(aq)\rightleftharpoons { [Cu{ ({ NH }_{ 3 }) }_{ 4 }] }_{ (aq) }^{ 2+ }$ among H2O and NH3 Which is stronger Lewis base.

18. A lab assistant prepared a solution by adding a calculated quantity of HCl gas 250C o to get a solution with [H3O+]= 4$\times$10-5M. Is the solution neutral (or) acidic (or) basic.

19. Calculate the concentration of OH- in a fruit juice which contains $2\times10^{-3}$ M, H3O+ ion. Identify the nature of the solution.

20. Calculate pH of 10-7M HCl

21. Define Buffer solution.

22. Define neutralisation reaction.

23. Magnesium is not precipitated from a solution of its salt by a mixture of NH4OH and NH4Cl. Explain

24. BF3 is termed as an acid though it does not contain H+ ions. Explain.

25. Why is aqueous solution of FeCl3 acidic?

1. 3 Marks

10 x 3 = 30
26. Explain common ion effect with an example

27. 50ml of 0.05M HNO3 is added to 50ml of 0.025M KOH. Calculate the pH of the resultant solution.

28. Derive an expression for the hydrolysis constant and degree of hydrolysis of salt of strong acid and weak base

29. A solution of 0.10M of a weak electrolyte is found to be dissociated to the extent of 1.20% at 25oC . Find the dissociation constant of the acid.

30.  Fine the pH of a buffer solution containing 0.20 mole per litre sodium acetate and 0.18 mole per litre acetic acid. Ka for acetic acid is $1.8\times10^{-5}$.

31. Based on Arrhenius concept, defme acid and bases and give an example for each.

32. What do you mean by auto ionisation of water?

33. For an aqueous solution of NH4CI, prove that [H+ ] = $\sqrt { { K }_{ n }.C }$

34. What is Henderson equation?

35. What do you mean by buffer action?

1. 5 Marks

7 x 5 = 35
36. Solubility product of Ag2 CrO4 4 is $1\times10^{-12}$.What is the solubility of Ag2 CrO4 in 0.01M AgNO3 solution?

37. A particular saturated solution of silver chromate Ag2 CrO4 has $[Ag^{+}]=5\times10^{-5}$ and $[CrO_{4}]^{2-}=4.4\times10^{-4}M$.What is the value of Ksp for Ag2 CrO4?

38. Establish a relationship between the solubility product and molar solubility for the following
a) BaSO b)Ag2(CrO4)

39. Calculate the pH of solution with HO+ concentrations in mol dm-3.
(i) 10-4
(ii) 10-7
(iii) 6.8 x 10-3
(iv) 3.2 x 10-5
(v) 0.035
(vi) 0.25
(vii) 5.4 x 10-9
(viii) 7.1 x 10-7

40. Calculate the Kb for ammonium hydroxide given its degree of dissociation to be 0.042 in 0.01 Nsolution.

41. Calculate the pH of 0.01 MNaOH.

42. Derive the hydrolysis constant for the hydrolysis of salt of strong base and weak acid. Deduce its pH