Chemical Equilibrium MCQ Questions & Answers in Physical Chemistry | Chemistry
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31.
One mole of $${O_2}\left( g \right)$$ and two moles of $$S{O_2}\left( g \right)$$ were heated in a closed vessel of one-litre capacity at $$1098\,K.$$ At equilibrium $$1.6\,moles$$ of $$S{O_3}\left( g \right)$$ were found. The equilibrium constant $${K_c}$$ of the
reaction would be
32.
For the reaction : $${H_{2\left( g \right)}} + {I_{2\left( g \right)}} \rightleftharpoons 2H{I_{\left( g \right)}},$$ the standard free energy is $$\Delta {G^ \circ } > 0.$$ The equilibrium constant $$(K)$$ would be ___________.
33.
At $${527^ \circ }C,$$ the reaction given below has $${K_c} = 4$$
$$N{H_3}\left( g \right) \rightleftharpoons \frac{1}{2}{N_2}\left( g \right) + \frac{3}{2}{H_2}\left( g \right)$$
What is the $${K_P}$$ for the reaction ?
$${N_2}\left( g \right) + 3{H_2}\left( g \right) \rightleftharpoons 2N{H_3}\left( g \right)$$
A
$$16 \times {\left( {800R} \right)^2}$$
B
$${\left( {\frac{{800R}}{4}} \right)^{ - 2}}$$
C
$${\left( {\frac{1}{{4 \times 800R}}} \right)^2}$$
34.
What is the equilibrium expression for the reaction $${P_4}\left( s \right) + 5{O_2}\left( g \right) \rightleftharpoons {P_4}{O_{10}}\left( s \right)?$$
A
$${K_c} = {\left[ {{O_2}} \right]^5}$$
B
$${K_c} = \frac{{\left[ {{P_4}{O_{10}}} \right]}}{{5\left[ {{P_4}} \right]\left[ {{O_2}} \right]}}$$
C
$${K_c} = \frac{{\left[ {{P_4}{O_{10}}} \right]}}{{\left[ {{P_4}} \right]{{\left[ {{O_2}} \right]}^5}}}$$
D
$${K_c} = \frac{1}{{{{\left[ {{O_2}} \right]}^5}}}$$
For $${P_4}\left( s \right) + 5{O_2}\left( g \right) \rightleftharpoons {P_4}{O_{10}}\left( s \right)$$
$${K_c} = \frac{1}{{{{\left( {{O_2}} \right)}^5}}}.$$ The solids have concentration unity
35.
On increasing the pressure, in which direction will the gas phase reaction proceed to re-establish equilibrium, is predicted by applying the Le Chatelier's principle. Consider the reaction : $${N_{2\left( g \right)}} + 3{H_{2\left( g \right)}} \rightleftharpoons 2N{H_{3\left( g \right)}}$$
Which of the following is correct, if the total pressure at which the equilibrium is established, is increased without changing the temperature?
A
$$K$$ will remain same.
B
$$K$$ will decrease.
C
$$K$$ will increase.
D
$$K$$ will increase initially and decrease when pressure is very high.
Answer :
$$K$$ will remain same.
Equilibrium constant $$(K)$$ is temperature dependent as temperature is constant thus, $$K$$ will remain same.
36.
What will be the correct order of vapour pressure of water, acetone and ether $$30{\,^ \circ }C.$$ Given that among these compounds, water has maximum boiling point and ether has minimum boiling point?
A
Water < Ether < Acetone
B
Water < Acetone < Ether
C
Ether < Acetone < Water
D
Acetone < Ether < Water
Answer :
Water < Acetone < Ether
Higher the boiling point lower will be the vapour pressure. Thus, the correct order of vapour pressure is $$\mathop {{\text{Water }}}\limits_{{\text{(max}}{\text{. b}}{\text{.pt}}{\text{.}})} {\text{ < Acetone < }}\mathop {{\text{ Ether}}}\limits_{{\text{(min}}{\text{. b}}{\text{.pt}}{\text{.)}}} $$
37.
In the following reaction :
$$2N{O_{\left( g \right)}} + C{l_{2\left( g \right)}} \rightleftharpoons 2NOC{l_{\left( g \right)}}$$
it is observed that equilibrium is not attained and the rate of forward reaction is greater than rate of backward reaction. Which of the following is true for the reaction?
A
$${K_p} = {Q_p}$$
B
$${Q_p} > {K_p}$$
C
$${Q_p} < {K_p}$$
D
$${Q_p} = 0$$
Answer :
$${Q_p} < {K_p}$$
When $${Q_p} < {K_p},$$ the rate of forward reaction is more than rate of backward reaction.
38.
The following reaction is at equilibrium,
$$\mathop {Fe_{\left( {aq} \right)}^{3 + }}\limits_{{\text{Yellow}}} + \mathop {SCN_{\left( {aq} \right)}^ - }\limits_{{\text{Colourless}}} \rightleftharpoons \mathop {\left[ {Fe\left( {SCN} \right)} \right]_{\left( {aq} \right)}^{2 + }}\limits_{{\text{Deep}}\,{\text{red}}} ;$$ $${K_c} = \frac{{{{\left[ {Fe\left( {SCN} \right)} \right]}^{2 + }}}}{{\left[ {F{e^{3 + }}} \right]\left[ {SC{N^ - }} \right]}}$$
In the above reaction, colour intensity of red colour can be increased by
A
addition of $$KSCN$$
B
addition of oxalic acid which reacts with $$F{e^{3 + }}$$ ions
C
addition of $$H{g^{2 + }}$$ ions which react with $$SC{N^ - }$$ ions
D
red colour intensity cannot be changed.
Answer :
addition of $$KSCN$$
Addition of $$KSCN$$ increases the colour intensity of the solution as it shifts the equilibrium to right. Addition of reagents like oxalic acid or $$H{g^{2 + }}$$ ions which remove $$F{e^{3 + }}$$ or $$SC{N^ - }$$ ions shift the equilibrium to the left and colour intensity decreases.
39.
For the reaction, $$2S{O_{2\left( g \right)}} + {O_{2\left( g \right)}} \rightleftharpoons 2S{O_{3\left( g \right)}},$$ what is $${K_c}$$ when the equilibrium concentration of $$\left[ {S{O_2}} \right] = 0.60\,M,\left[ {{O_2}} \right] = 0.82\,M$$ and $$\left[ {S{O_3}} \right] = 1.90\,M?$$
40.
Consider the expression $$\Delta G = - RT\ln {K_p} + RT\ln {Q_p}$$ and indicate the correct statement at equilibrium
A
$$\Delta G = 0,{Q_p} > {K_p}$$ the equilibrium reaction will shift from left to right
B
$$\Delta G = 0,{Q_p} = {K_p}$$ the equilibrium reaction will shift from left to right
C
$$\Delta G = \infty ,{Q_p} < {K_p}$$ the equilibrium reaction will
shift from right to left
D
$$\Delta G < 0,{Q_p} > {K_p}$$ the equilibrium reaction will shift from right to left where $${Q_p}$$ and $${K_p}$$ term refer to reaction quotient and equilibrium constant at constant pressure respectively.
Answer :
$$\Delta G = 0,{Q_p} = {K_p}$$ the equilibrium reaction will shift from left to right
Van’t Hoff reaction isotherm is $$\Delta G = \Delta {G^ \circ } + RT$$
$$\ln \,Qp$$
When the reaction is in a state of equilibrium
$$\Delta G = 0$$
Then $$\Delta {G^ \circ } = - RT\,\ln \,{Q_p} = - RT\,\ln \,{K_p}$$