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1

NEET 2017

MCQ (Single Correct Answer)
A 20 litre container at 400 K contains CO2(g) at pressure 0.4 atm and an excess of SrO (neglect the volume of solid SrO). The volume of the container is now decreased by moving the movable piston fitted in the container. The maximum volume of the container, when pressure of CO2 attains its maximum value, will be

(Given that : SrCO3(s) $$\rightleftharpoons$$ SrO(s) + CO2(g), Kp = 1.6 atm)
A
10 litre
B
4 litre
C
2 litre
D
5 litre

Explanation

Initially, P1 = 0.4 atm

V1 = 20 L

T1 = 400 K

Max. pressure of CO2 = Pressure of CO2 at equilibrium

For reaction,

SrCO3(s) ⇌ SrO(s) + CO2

Kp = PCO2 = 1.6 atm = maximum pressure of CO2 volume of container at this stage.

V2 = $${{nRT} \over {{P_2}}}$$ ......(i)

Since, reaction was not at equilibrium earlier and also container is sealed.

$$ \therefore $$ n = constant

n = $${{{P_1}{V_1}} \over {RT}}$$ .....(ii)

From (i) and (ii)

V2 = $${{{P_1}{V_1}} \over {RT}} \times {{RT} \over {{P_2}}}$$ = $${{0.4 \times 20} \over {1.6}}$$ = 5 L
2

NEET 2017

MCQ (Single Correct Answer)
Concentration of the Ag+ ions in a saturated solution of Ag2C2O4 is 2.2 $$ \times $$ 10$$-$$4 mol L$$-$$1. Solubility product of Ag2C2O4 is
A
2.66 $$ \times $$ 10$$-$$12
B
4.5 $$ \times $$ 10$$-$$11
C
5.3 $$ \times $$ 10$$-$$12
D
2.42 $$ \times $$ 10$$-$$8

Explanation

Ag2C2O4(s) $$ \to $$ 2Ag+ + C2O4 2–
      S                  2S           S

Ksp = [Ag+] 2 [C2O4 2–] = [2S]2 [S]

[Ag+] = 2S = 2.2 × 10–4

or S = 1.1 × 10–4 M

$$ \therefore $$ Ksp = [2.2 × 10–4 ]2 [1.1 × 10–4] = 5.3 × 10–12
3

NEET 2017

MCQ (Single Correct Answer)
The equilibrium constants of the following are

N2 + 3H2 $$\rightleftharpoons$$ 2NH3;     K1

N2 + O2 $$\rightleftharpoons$$ 2NO;     K2

H2 + $${1 \over 2}$$O2 $$\rightleftharpoons$$ H2O;     K3

The equilibrium constant (K) of the reaction :

2NH3 + $${5 \over 2}$$ O2 $$\rightleftharpoons$$ 2NO + 3H2O will be
A
K2K33/K1
B
K2K3/K1
C
K23K3/K1
D
K1K33/K2

Explanation

2NH3 $$\rightleftharpoons$$ N2 + 3H2;     $${1 \over {{K_1}}}$$

N2 + O2 $$\rightleftharpoons$$ 2NO;     K2

3H2 + $${3 \over 2}$$O2 $$\rightleftharpoons$$ 3H2O;     (K3)3

By adding all equations, we get

2NH3 + $${5 \over 2}$$ O2 $$\rightleftharpoons$$ 2NO + 3H2O

$$ \therefore $$ K = $${{{K_2} \times {{\left( {{K_3}} \right)}^3}} \over {{K_1}}}$$
4

NEET 2016 Phase 1

MCQ (Single Correct Answer)
MY and NY3, two nearly insoluble salts, have the same Ksp values of 6.2 $$ \times $$ 10$$-$$13 at room temperature. Which statement would be true in regard to MY and NY3?
A
The salts MY and NY3 are more soluble in 0.5 M KY than in pure water.
B
The addition of the salt of KY to solution of MY and NY3 will have no effect on their solubilities.
C
The molar solubilities of MY and NY3 in water are identical.
D
The molar solubility of MY in water is less than that of NY3.

Explanation

MY ⇌ M+ + Y
   s        s       s

Ksp = s.s = s2

$$ \Rightarrow $$ s = $$\sqrt {6.2 \times {{10}^{ - 13}}} $$

= 7.87 × 10–7 mol L–1

NY3 ⇌ N+ + 3Y
   s        s       3s

Ksp = s.(3s)3 = 27s4

6.2 × 10–13 = 27s4

$$ \Rightarrow $$ s = 3.89 × 10–4 mol L–1

Hence, molar solubility of MY in water is less than that of NY3.

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