1
MCQ (Single Correct Answer)

AIPMT 2007

A weak acid, HA, has a Ka of 1.00 $$ \times $$ 10$$-$$5. If 0.100 mol of this acid is dissolved in one litre of water, the percentage of acid dissociated at equilibrium is closest to
A
1.00%
B
99.9%
C
0.100%
D
99.0%

Explanation

For weak acid degree of dissociation,

$$\alpha $$ = $$\sqrt {{{{K_a}} \over C}} $$

= $$\sqrt {{{1 \times {{10}^{ - 5}}} \over {0.1}}} = {10^{ - 2}}$$ = 1.00 %
2
MCQ (Single Correct Answer)

AIPMT 2007

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 = $${{{K_2} \times {{\left( {{K_3}} \right)}^3}} \over {{K_1}}}$$
3
MCQ (Single Correct Answer)

AIPMT 2006

For the reaction :
CH4(g) + 2O2(g) $$\rightleftharpoons$$ CO2(g) + 2H2O(l),
$$\Delta $$Hr = $$-$$ 170.8 kJ mol$$-$$1.
Which of the following statements is not true?
A
The reaction is exothermic.
B
At equilibrium, the concentrations of CO2(g) and H2O(l) are not equal.
C
The equilibrium constant for the reaction is given by Kp = $${{\left[ {C{O_2}} \right]} \over {\left[ {C{H_4}} \right]\left[ {{O_2}} \right]}}$$
D
Addition of CH4(g) or O2(g) at equilibrium will cause a shift to the right.

Explanation

Option C is incorrect as the value of KP given is wrong. It should have been

KP = $${{{P_{C{O_2}}}} \over {{P_{C{H_4}}} \times {{\left[ {{P_{{O_2}}}} \right]}^2}}}$$
4
MCQ (Single Correct Answer)

AIPMT 2006

The hydrogen ion concentration of a 10$$-$$8 M, HCl aqueous solution at 298 K (Kw = 10$$-$$14) is
A
1.0 $$ \times $$ 10$$-$$8 M
B
1.0 $$ \times $$ 10$$-$$6 M
C
1.0525 $$ \times $$ 10$$-$$7 M
D
9.525 $$ \times $$ 10$$-$$8 M

Explanation

In HCl solution [H+] = 10-8 M

Also from water, [H+] = 10-7 M

$$ \therefore $$ Total [H+] = 10-8 M + 10-7 M

= 1.1 ×10–7 M

$$ \simeq $$ 1.0525 $$ \times $$ 10$$-$$7 M

EXAM MAP

Joint Entrance Examination

JEE Advanced JEE Main

Graduate Aptitude Test in Engineering

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

Medical

NEET

CBSE

Class 12