Chemical Equilibrium MCQ Questions & Answers in Physical Chemistry | Chemistry
Learn Chemical Equilibrium MCQ questions & answers in Physical Chemistry are available for students perparing for IIT-JEE, NEET, Engineering and Medical Enternace exam.
51.
The equilibrium constant for the following reaction will be $${P_{4\left( s \right)}} + 5{O_{2\left( g \right)}} \rightleftharpoons {P_4}{O_{10\left( s \right)}}$$
A
$${K_c} = \frac{{\left[ {{P_4}} \right]{{\left[ {{O_2}} \right]}^5}}}{{\left[ {{P_4}{O_{10}}} \right]}}$$
B
$${K_c} = \frac{1}{{{{\left[ {{O_2}} \right]}^5}}}$$
C
$${K_c} = \frac{{\left[ {{P_4}{O_{10}}} \right]}}{{\left[ {{P_4}} \right]{{\left[ {{O_2}} \right]}^5}}}$$
$${P_{4\left( s \right)}} + 5{O_{2\left( g \right)}} \rightleftharpoons {P_4}{O_{10\left( s \right)}}$$
Since concentration of solids is taken as 1, expression for equilibrium constant involves only oxygen.
$${K_c} = \frac{1}{{{{\left[ {{O_2}} \right]}^5}}}$$
52.
A reaction is said to be in equilibrium when
A
the rate of transformation of reactants to products is equal to the rate of transformation of products to the reactants
B
50% of the reactants are converted to products
C
the reaction is near completion and all the reactants are converted to products
D
the volume of reactants is just equal to the volume of the products.
Answer :
the rate of transformation of reactants to products is equal to the rate of transformation of products to the reactants
A reaction is said to be in equilibrium when rate of forward reaction is equal to the rate of backward reaction.
53.
$$8\,mol$$ of $$A{B_3}\left( g \right)$$ are introduced into a $$1.0\,d{m^3}$$ vessel. If it dissociates as $$2A{B_3}\left( g \right) \rightleftharpoons {A_2}\left( g \right) + 3{B_2}\left( g \right).$$ At equilibrium, $$2\,mol$$ of $${A_2}$$ are found to be present. The equilibrium constant of this reaction is
54.
The equilibrium constant $$\left( {{K_c}} \right)$$ for the reaction $${N_2}\left( g \right) + {O_2}\left( g \right) \to 2NO\left( g \right)$$ at temperature $$T$$ is 4 × 10-4. The value of $${{K_c}}$$ for the reaction
$$NO\left( g \right) \to \frac{1}{2}{N_2}\left( g \right) + \frac{1}{2}{O_2}\left( g \right)$$ at the same temperature is :
A
0.02
B
2.5 × 102
C
4 × 10-4
D
50.0
Answer :
50.0
$$\eqalign{
& {\text{For the reaction}} \cr
& {N_2} + {\text{ }}{O_2} \to 2NO\,\,\,\,\,\,\,\,\,\,K = 4 \times {10^{ - 4}} \cr
& {\text{Hence for the reaction}} \cr
& NO \to \frac{1}{2}{N_2} + \frac{1}{2}{O_2}\,\,\,\,\,\,\,K' = \frac{1}{{\sqrt K }} = \frac{1}{{\sqrt {4 \times {{10}^{ - 4}}} }} = 50 \cr} $$
55.
If the synthesis of ammonia from Haber's process is carried out with exactly the same starting conditions ( of partial pressure and temperature ) but using $${D_2}$$ (deuterium) in place of $${H_2}.$$ Then
A
the equilibrium will be disturbed
B
the composition of reaction mixture will remain same at equilibrium.
C
Use of isotope in reaction will not produce ammonia.
D
At equilibrium rate of forward reaction will be greater than the rate of reverse reaction
Answer :
the composition of reaction mixture will remain same at equilibrium.
The reaction mixtures starting either with $${H_2}$$ or $${D_2}$$ reach equilibrium with the same composition, except that $${D_2}$$ and $$N{D_3}$$ are present instead of $${H_2}$$ and $$N{H_3}.$$
56.
Which of the following is not a general characteristic of equilibria involving physical processes ?
A
Equilibrium is possible only in a closed system at a given temperature.
B
All measurable properties of the system remain constant.
C
All the physical processes stop at equilibrium.
D
The opposing processes occur at the same rate and there is dynamic but stable condition.
Answer :
All the physical processes stop at equilibrium.
All the physical processes do not stop at equilibrium
57.
On the basis of Le-Chatelier's principle, predict which of the following conditions would be unfavourable for the formation of $$S{O_3}?$$ Given that $$2S{O_2} + {O_2} \rightleftharpoons 2S{O_3};\Delta H = - 42\,kcal$$
A
Low pressure and low temperature
B
High pressure and low temperature
C
High temperature and low pressure
D
High concentration of $$S{O_2}$$
Answer :
High temperature and low pressure
Since reaction is exothermic hence low temperature will favour forward reaction
also volume is decreased by applying high pressure.
58.
Some inert gas is added at constant volume to the following reaction at equilibrium
$$N{H_4}HS\left( s \right) \rightleftharpoons N{H_3}\left( g \right) + {H_2}S\left( g \right)$$
Predict the effect of adding the inert gas :
A
The equilibrium shifts in the forward direction
B
The equilibrium shifts in the backward direction
C
The equilibrium remains unaffected
D
The value of $${K_P}$$ is increased
Answer :
The equilibrium remains unaffected
Addition of inert gas at constant volume has no effect on equilibrium.
59.
A mixture of $$1.57\,mol$$ of $${N_2},1.92\,mol$$ of $${H_2}$$ and $$8.13\,mol$$ of $$N{H_3}$$ is introduced into $$20\,L$$ reaction vessel at $$500\,K.$$ At this temperature, the equilibrium constant, $${K_c}$$ for the reaction, $${N_{2\left( g \right)}} + 3{H_{2\left( g \right)}} \rightleftharpoons 2N{H_{3\left( g \right)}}$$ is $$1.7 \times {10^2}.$$ What is the direction of the net reaction?
A
Forward
B
Backward
C
At equilibrium
D
Data is insufficient
Answer :
Backward
The reaction is $${N_{2\left( g \right)}} + 3{H_{2\left( g \right)}} \rightleftharpoons 2N{H_{3\left( g \right)}}$$
$$\eqalign{
& {Q_c} = \frac{{{{\left[ {N{H_3}} \right]}^2}}}{{\left[ {{N_2}} \right]{{\left[ {{H_2}} \right]}^3}}} \cr
& \,\,\,\,\,\,\,\, = \frac{{{{\left( {\frac{{8.13}}{{20}}\,mol\,{L^{ - 1}}} \right)}^2}}}{{\left( {\frac{{1.57}}{{20}}\,mol\,{L^{ - 1}}} \right){{\left( {\frac{{1.92}}{{20}}\,mol\,{L^{ - 1}}} \right)}^3}}} \cr
& \,\,\,\,\,\,\,\, = 2.38 \times {10^3} \cr} $$
As $${Q_c} \ne {K_c},$$ the reaction mixture is not in equilibrium.
As $${Q_c} > {K_c},$$ the net reaction will be in the backward direction.
60.
The dissociation constants for acetic acid and $$HCN$$ at $${25^ \circ }C$$ are $$1.5 \times {10^{ - 5}}$$ and $$4.5 \times {10^{ - 10}},$$ respectively. The equilibrium constant for the equilibrium, $$C{N^ - } + C{H_3}COOH \rightleftharpoons $$ $$HCN + C{H_3}CO{O^ - }$$ would be