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Question: For the reaction, \(A + B \rightleftharpoons 3C\) , at \({25^o}C\) , \(3litre\) vessel contains \(1,...

For the reaction, A+B⇌3CA + B \rightleftharpoons 3C , at 25oC{25^o}C , 3litre3litre vessel contains 1,2,41,2,4 moles of A,BA,B and CC respectively. If Kc{K_c} for the reaction is 1010 , the reaction will proceed in:
A. forward reaction
B. backward reaction
C. in either direction
D. in equilibrium

Explanation

Solution

In chemical thermodynamics, the reaction quotient (QQ ) is a quantity that provides a measurement of the relative quantities of products and reactants present in a reaction mixture for a reaction with well-defined overall stoichiometry, at a particular point in time. Mathematically, it is defined as the ratio of the activities (or molar concentrations) of the product species over those of the reactant species involved in the chemical reaction, taking stoichiometric coefficients of the reaction into account as exponents of the concentrations.

Complete step by step answer:
According to the question, the reaction mentioned is as follows:
A+B⇌3CA + B \rightleftharpoons 3C
Concentration of a substance is defined as the number of moles of the substance in a given liter of solution.
The concentration of A=[13]mol/lA = \left[ {\dfrac{1}{3}} \right]mol/l
The concentration of B=[23]mol/lB = \left[ {\dfrac{2}{3}} \right]mol/l
The concentration of C=[43]mol/lC = \left[ {\dfrac{4}{3}} \right]mol/l
The reaction quotient (Q)=[C]3[A][B]=[43]3[13][23]=10.66(Q) = \dfrac{{{{[C]}^3}}}{{[A][B]}} = \dfrac{{{{\left[ {\dfrac{4}{3}} \right]}^3}}}{{\left[ {\dfrac{1}{3}} \right]\left[ {\dfrac{2}{3}} \right]}} = 10.66
As per the question, the value of equilibrium constant (Kc)=10({K_c}) = 10
Thus, in order to attain the value of equilibrium constant, the value of reaction quotient must decrease to 10. This indicates that the reaction should move in a reverse direction or backward direction. This means that the above reaction is of backward nature.
Thus, the correct option is B. backward reaction.

Note:
When the reaction proceeds from the reactant side to the product side, this means that the reaction is moving in a forward direction. In the case of backward or reversible reaction, the direction of reaction is from the product side to the reactant side.