Question

At 783K in the reaction, ${H_2}\left( g \right) + {I_2}\left( g \right) \Leftrightarrow 2HI\left( g \right)$ the molar concentrations ($mo{l^{ - 1}}$) of ${H_2}$, ${I_2}$​ and $HI$ at some
Instant of time are $0.1$, $0.2$ and $0.4$ respectively. If the equilibrium constant is $46$ at the
same temperature, then as the reaction proceeds:
(A) The amount of ${H_2}$ will increase
(B) The amount of s will decrease
(C) The amount of ${H_2}$ and ${I_2}$ will increase
(D) The amount of ${H_2}$ and ${I_2}$ will not change

Answer 1

To solve this, we need to calculate the reaction quotient and compare it with the given equilibrium constant and then we can tell whether the reaction will move in the forward direction or backward direction.
Reaction Quotient: It is defined as the quantity used to determine the concentration of reactants
and products at a point of time in a reaction. It is denoted by $'Q'$.
For a Reaction, $aA + bB \Leftrightarrow cC + dD$ the reaction quotient $'Q'$ is given as
$Q = \dfrac{{{{\left[ C \right]}^c}{{\left[ D \right]}^d}}}{{{{\left[ A \right]}^a}{{\left[ B \right]}^b}}}$
Where, $c = moles\,of\,C$, $d = moles\,of\,D$, $a = moles\,of\,A$ , $b = moles\,of\,B$

Complete step by step answer:
For the given reaction:
${H_2}\left( g \right) + {I_2}\left( g \right) \Leftrightarrow 2HI\left( g \right)$ , $k(\text{equilibrium constant)} = 46$
Molar concentrations of ${H_2} = 0.1$ , ${I_2} = 0.2$ and $HI = 0.4$
Now, we will calculate the reaction quotient and compare it with the equilibrium constant.
$'Q'$for the given reaction will be:
$Q = \dfrac{{{{\left[ {HI} \right]}^2}}}{{\left[ {{H_2}} \right]\left[ {{I_2}} \right]}}$
$\Rightarrow Q = \dfrac{{{{\left[ {0.4} \right]}^2}}}{{\left[ {0.1} \right]\left[ {0.2} \right]}}$
$Q = 8$
So, The reaction quotient is $8$ , an equilibrium constant is $46$ .
On comparing, we get $Q < K$.
Hence, the reaction will move in the forward direction which means the rate of product formation
will be high, and more $HI$ formation will take place.
Therefore, Option (A) is the correct choice.
Thus the correct option is (A) mixture consists of ${K_2}S{O_4}{\text{ }}and{\text{ }}MgB{r_2}$.

Note:
Equilibrium constant: It is defined as the value of reaction constant when the reaction
attains chemical equilibrium. In this state, the rate of reaction in the forward direction becomes equal to the rate of reaction in a backward direction. It is affected by many factors such as a change in temperature, change in molar concentrations of the reactants, or change in pressure. Comparing the value of reaction quotient and equilibrium constant if $Q < K$ then the reaction will take place in
forwarding direction means it will favor product formation. If $Q > K$ then the reaction will take
place in a backward direction means it will favor reactant formation.