121.
When hydrochloric acid is added to cobalt nitrate solution at room temperature, the following reaction takes place and the reaction mixture becomes blue. On cooling the mixture, it becomes pink. On the basis of this information mark the correct answer. $$\mathop {\left[ {Co{{\left( {{H_2}O} \right)}_6}} \right]_{\left( {aq} \right)}^{3 + }}\limits_{{\text{Pink}}} + 4Cl_{\left( {aq} \right)}^ - \rightleftharpoons $$ $$\mathop {\left[ {CoC{l_4}} \right]_{\left( {aq} \right)}^{2 - }}\limits_{{\text{Blue}}} + 6{H_2}{O_{\left( l \right)}}$$
A
$$\Delta H > 0$$ for the reaction
B
$$\Delta H < 0$$ for the reaction
C
$$\Delta H = 0$$ for the reaction
D
The sign of $$\Delta H$$ cannot be predicted on the basis of this information.
$$\mathop {\left[ {Co{{\left( {{H_2}O} \right)}_6}} \right]_{\left( {aq} \right)}^{3 + }}\limits_{{\text{Pink}}} + 4Cl_{\left( {aq} \right)}^ - \rightleftharpoons $$ $$\mathop {\left[ {CoC{l_4}} \right]_{\left( {aq} \right)}^{2 - }}\limits_{{\text{Blue}}} + 6{H_2}{O_{\left( l \right)}}$$
On cooling the mixture, the reaction proceeds in backward direction and on heating the mixture, the reaction proceeds in forward direction, hence, the reaction is endothermic i.e., $$\Delta H > 0.$$
122.
The solubility in water of a sparingly soluble salt $$A{B_2}$$ is $$1.0 \times {10^{ - 5}}mol\,{L^{ - 1}}.$$ Its solubility product number will be
123.
The equilibrium constant for the reaction
$$\eqalign{
& S{O_3}\left( g \right) \rightleftharpoons S{O_2}\left( g \right) + \frac{1}{2}{O_2}\left( g \right) \cr
& {\text{is}}\,{K_c} = 4.9 \times {10^{ - 2}}.\,{\text{The value of }}{{\text{K}}_c}{\text{ for the reaction}} \cr
& {\text{2S}}{{\text{O}}_2}\left( g \right) + {O_2}\left( g \right) \rightleftharpoons 2S{O_3}\left( g \right) \cr
& {\text{will}}\,{\text{be}} \cr} $$
A
$${\text{9}}{\text{.8}} \times {\text{1}}{{\text{0}}^{ - 2}}$$
When we add heat to the equilibrium between solid and liquid, then the equilibrium shifts towards liquid and hence, the amount of solid decrease and amount of liquid increase.
126.
When two reactants, $$A$$ & $$B$$ are mixed to give products $$C$$ & $$D,$$ the reaction quotient $$Q,$$ at the initial stages of the reaction
At initial stage of reaction, concentration of each product will increase and hence $$Q$$ will increase.
127.
At constant temperature, the equilibrium constant $$\left( {{K_p}} \right)$$ for the decomposition reaction $${N_2}{O_4} \rightleftharpoons 2N{O_2}$$ is expressed by $${K_p} = \frac{{\left( {4{x^2}P} \right)}}{{\left( {1 - {x^2}} \right)}},$$ where $$P$$ = pressure, $$x$$ = extent of decomposition. Which one of the following statements is true?
A
$${{K_p}}$$ increases with increase of $$P$$
B
$${{K_p}}$$ increases with increase of $$x$$
C
$${{K_p}}$$ increases with decrease of $$x$$
D
$${{K_p}}$$ remains constant with change in $$P$$ and $$x$$
Answer :
$${{K_p}}$$ remains constant with change in $$P$$ and $$x$$
At constant temperature $${{K_p}}$$ pressure constant. With change of pressure, $$x$$ will change in such a way that $${{K_p}}$$ remains a constant.
128.
The equilibrium constant for the reaction $$W + X \rightleftharpoons Y + Z$$ is 9. If one mole of each of $$w$$ and $$x$$ are mixed and there is no change in volume, the number of moles of $$y$$ formed is
129.
The Haber’s process for the formation of $$N{H_3}$$ at $$298K$$ is $${N_2} + 3{H_2} \rightleftharpoons 2N{H_3}\,;\Delta H = - 46.0\,kJ;$$ Which of the following is the correct statement
A
The condition for equilibrium is $${G_{{N_2}}} + 3{G_{{H_2}}} = 2{G_{N{H_3}}}.$$ where $$G$$ is Gibb's free energy per mole of the gaseous species measured at that partial pressure.
B
On adding $${N_2}$$ , the equilibrium will shift to forward direction because according to IInd law of thermodynamics the entropy must increase in the direction of spontaneous reaction
C
The catalyst will increase the rate of forward reaction by 2 times and that of backward reaction by 1.5 times
D
None of these
Answer :
The condition for equilibrium is $${G_{{N_2}}} + 3{G_{{H_2}}} = 2{G_{N{H_3}}}.$$ where $$G$$ is Gibb's free energy per mole of the gaseous species measured at that partial pressure.
In a reversible reaction, catalyst speeds up both the forward and backward reactions to the same extent, so (C) is wrong. At equilibrium,
$$\eqalign{
& \Delta G = {G_{{\text{poducts}}}} - {G_{{\text{reactants}}}} = 0 \cr
& \Rightarrow 2{G_{N{H_3}}} - \left( {{G_{{N_2}}} + 3{G_{{H_2}}}} \right) = 0 \cr
& or\,\,2{G_{N{H_3}}} = {G_{{N_2}}} + 3{G_{{H_2}}} \cr} $$
130.
For a reversible reaction at $$298\,K$$ the equilibrium constant $$K$$ is 200. What is the value of $$\Delta {G^ \circ }$$ at $$298\,K?$$