1
MCQ (Single Correct Answer)

AIPMT 2001

Ionisation constant of CH3COOH is 1.7 $$ \times $$ 10$$-$$5 and concentration of H+ ions is 3.4 $$ \times $$ 10$$-$$4. Then find out initial concentration of CH3COOH molecules.
A
3.4 $$ \times $$ 10$$-$$4
B
3.4 $$ \times $$ 10$$-$$3
C
6.8 $$ \times $$ 10$$-$$4
D
6.8 $$ \times $$ 10$$-$$3

Explanation

CH3COOH ⇌ CH3COO + H+

Kc = $${{{\left[ {C{H_3}CO{O^ - }} \right]\left[ {{H^ + }} \right]} \over {\left[ {C{H_3}COOH} \right]}}}$$

$$ \Rightarrow $$ [CH3COOH] = $${{{3.4 \times {{10}^{ - 4}} \times 3.4 \times {{10}^{ - 4}}} \over {1.7 \times {{10}^{ - 5}}}}}$$

= 6.8 × 10–3
2
MCQ (Single Correct Answer)

AIPMT 2001

In HS$$-$$, I$$-$$, R $$-$$ NH2, NH3 order of proton accepting tendency will be
A
I$$-$$ > NH3 > R $$-$$ NH2 > HS$$-$$
B
NH3 > R $$-$$ NH2 > HS$$-$$ > I$$-$$
C
R $$-$$ NH2 > NH3 > HS$$-$$ > I$$-$$
D
HS$$-$$ > R $$-$$ NH2 > NH3 > I$$-$$

Explanation

Strong base has higher tendency to accept the proton. Increasing order of base and hence the order of accepting tendency of proton is

R $$-$$ NH2 > NH3 > HS$$-$$ > I$$-$$
3
MCQ (Single Correct Answer)

AIPMT 2000

Equilibrium constant Kp for following reaction
MgCO3(s) $$\rightleftharpoons$$ MgO(s) + CO2(g)
A
Kp = PCO2
B
Kp = PCO2 $$ \times $$ $${{{P_{C{O_2}}} \times {P_{MgO}}} \over {{P_{MgC{O_3}}}}}$$
C
Kp = $${{{P_{C{O_2}}} + {P_{MgO}}} \over {{P_{MgC{O_3}}}}}$$
D
Kp = $${{{P_{MgC{O_3}}}} \over {{P_{C{O_2}}} + {P_{MgO}}}}$$

Explanation

Kp = PCO2

As solids do not exert pressure, so their partial pressure is taken as unity.
4
MCQ (Single Correct Answer)

AIPMT 2000

For any reversible reaction, if we increase concentration of the reactants, then effect on equilibrium constant
A
depends on amount of concentration
B
unchange
C
decrease
D
increase

Explanation

Equilibrium constant of a reaction is independent of the concentration of species involved in the reaction but dependent only on the temperature.

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