1
MCQ (Single Correct Answer)

AIPMT 2011 Mains

In qualitative analysis, the metals of group I can be separated from other ions by precipitating them as chloride salts. A solution initially contains Ag+ and pb2+ at a concentration of 0.10 M. Aqueous HCl is added to this solution until the Cl$$-$$ concentration is 0.10 M. What will the concentrations of Ag+ and Pb2+ be at equilibrium ?

(Ksp for AgCl = 1.8 $$ \times $$ 10$$-$$10, Ksp for PbCl2 = 1.7 $$ \times $$ 10$$-$$5)
A
[Ag+] = 1.8 $$ \times $$ 10$$-$$7 M, [Pb2+] = 1.7 $$ \times $$ 10$$-$$6 M
B
[Ag+] = 1.8 $$ \times $$ 10$$-$$11 M, [Pb2+] = 8.5 $$ \times $$ 10$$-$$5 M
C
[Ag+] = 1.8 $$ \times $$ 10$$-$$9 M, [Pb2+] = 1.7 $$ \times $$ 10$$-$$3 M
D
[Ag+] = 1.8 $$ \times $$ 10$$-$$11 M, [Pb2+] = 1.7 $$ \times $$ 10$$-$$4 M

Explanation

Ksp[AgCl] = [Ag+][Cl-]

$$ \Rightarrow $$ [Ag+] = $${{1.8 \times {{10}^{ - 10}}} \over {{{10}^{ - 1}}}}$$ = 1.8 $$ \times $$ 10$$-$$9 M

Ksp[PbCl2] = [Pb2+][Cl-]2

$$ \Rightarrow $$ [Pb2+] = $${{1.7 \times {{10}^{ - 5}}} \over {{{10}^{ - 1}} \times {{10}^{ - 1}}}}$$ = 1.7 $$ \times $$ 10$$-$$3 M
2
MCQ (Single Correct Answer)

AIPMT 2011 Prelims

For the reaction, N2(g) + O2(g) $$\rightleftharpoons$$ 2NO(g), the equilibrium constant is K1. The equilibrium constant is K2 for the reaction,
2NO(g) + O2(g) $$\rightleftharpoons$$ 2NO2(g)
What is K for the reaction,
NO2(g) $$\rightleftharpoons$$ $${1 \over 2}$$N2(g) + O2(g)
A
$${1 \over {2{K_1}{K_2}}}$$
B
$${1 \over {4{K_1}{K_2}}}$$
C
$${\left[ {{1 \over {{K_1}{K_2}}}} \right]^{1/2}}$$
D
$${1 \over {{K_1}{K_2}}}$$

Explanation

N2(g) + $${1 \over 2}$$O2(g) $$\rightleftharpoons$$ NO(g),     $${\left( {{K_1}} \right)^{{1 \over 2}}}$$

NO(g) + $${1 \over 2}$$O2(g) $$\rightleftharpoons$$ NO2(g),     $${\left( {{K_2}} \right)^{{1 \over 2}}}$$
---------------------------------------------------
$${1 \over 2}$$N2(g) + O2(g) $$\rightleftharpoons$$ NO2(g)    $${\left( {{K_1}{K_2}} \right)^{{1 \over 2}}}$$

So, for the reverse reaction which is the desired one the value of K will be reciprocal of this value. i.e.

K = $${\left[ {{1 \over {{K_1}{K_2}}}} \right]^{1/2}}$$
3
MCQ (Single Correct Answer)

AIPMT 2011 Prelims

Which of the following is least likely to behave as Lewis base?
A
H2O
B
NH3
C
BF3
D
OH$$-$$

Explanation

The species which have a lone pair of electrons to donate or a negative charge on it can act as a Lewis base. Here, N atom in NH3 and O atom in H2O have lone pair of electrons available for donation. In OH the negative charge on it results in to behave it as a Lewis base. But BF3 is an electron deficient species thus, it is least likely to behave as Lewis base.
4
MCQ (Single Correct Answer)

AIPMT 2011 Prelims

A buffer solution is prepared in which the concentration of NH3 is 0.30 M and the concentration of NH+4 is 0.20 M. If the equilibrium constant, Kb for NH3 equals 1.8 $$ \times $$ 10$$-$$5, what is the pH of this solution? (log 2.7 = 0.43)
A
9.08
B
9.43
C
11.72
D
8.73

Explanation

pOH = pKb + log $${{\left[ {Salt} \right]} \over {\left[ {Base} \right]}}$$

= – log Kb + log $${{\left[ {Salt} \right]} \over {\left[ {Base} \right]}}$$

= – log 1.8× 10–5 + log $${{0.20} \over {0.30}}$$

= 5 – 0.25 + (–0.176) = 4.57

Now, pH = 14 – pOH = 14 – 4.57 = 9.43

EXAM MAP

Joint Entrance Examination

JEE Advanced JEE Main

Medical

NEET

Graduate Aptitude Test in Engineering

GATE CE GATE ECE GATE ME GATE IN GATE EE GATE CSE GATE PI