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#### Ionic Equilibrium Model Question Paper

12th Standard EM

Reg.No. :
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Chemistry

Time : 01:00:00 Hrs
Total Marks : 35
6 x 1 = 6
1. Conjugate base for bronsted acids H2O and HF are

(a)

OH- and H2FH+ , respectively

(b)

H3O+ and F, respectively

(c)

OH- and F-, respectively

(d)

H3O+ and H2F+, respectively

2. 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

3. 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

4. Krepresents

(a)

ionic product constant of water

(b)

Solubility product of water

(c)

Equilibrium constant of water

(d)

Buffer index

5. pH of buffer depends upon concentration of

(a)

acid (H+)

(b)

Conjugate base (OH-)

(c)

Salt

(d)

acid (H+) and Conjugate base (OH-)

6. The conjugate base of HCIO is _________

(a)

ClO-

(b)

Cl-

(c)

H2ClO+

(d)

CIO

7. 2 x 2 = 4
8. Assertion: According to Bronsted concept. H2O is an a neutral substance.
Reason: H2O molecule can accept as well as donate a proton.
a) (A) and (R) are true and (R) is the correct explanation of (A)
b) Both (A) and (R) are true but (R) does not explain (A)
c) (A) is true but (R) is false
d) Both (A) and (R) are false

9. Assertion: The dissociation of acetic acid decreases on addition of sodium acetate.
Reason: It is due to common ion effect.
a) (A) and (R) are true and (R) is the correct explanation of (A)
b) Both (A) and (R) are true but (R) does not explain (A)
c) (A) is true but (R) is false
d) Both (A) and (R) are false

10. 2 x 2 = 4
11. 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.

12. Calculate the ionisation constant for the conjugate base of HF. Ionisation constant of HF at 298 K is 6.8 X 10-4

13. 2 x 3 = 6
14. Derive an expression for the hydrolysis constant and degree of hydrolysis of salt of strong acid and weak base

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

16. 3 x 5 = 15
17. Ksp of AgCl is $1.8\times10^{-10}$. Calculate molar solubility in 1 M AgNO3

18. 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

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