Question

Consider the following reaction and its equilibrium constant: SO2(g) + NO2(8) - SO3(g) + NO(g) Kc=0.33 A reaction mixture contains 1.0 mol L-1 SO2, 0.50 mol L-1 NO2,0.50 mol L-1 SO3, and 1.0 mol L-1 NO. Which of the following statements is TRUE concerning this system?

A) The reaction will shift in the direction of reactants.

B) The system is at equilibrium.

C) The reaction quotient will decrease.

D) The reaction will shift in the direction of products.

E) The equilibrium constant will decrease.

Answer 1

Answer:

Step 1: Explanation

Kc is defined as the amounts of products and reactants present at equilibrium in a reversible chemical reaction at a given temperature.

Reaction quotient (Qc) is defined as the amounts of products and reactants in a chemical reaction at a given point in time.

To predict the direction of equilibrium of a reaction, the reaction quotient is used.

The reaction quotient, Qc, is calculated in the same way as the equilibrium constant calculated by using the current concentrations.

Once found, the reaction quotient is compared to the equilibrium constant such as

• If Qc < Kc, there there are more reactants present than equilibrium and reaction will shift to the right i.e proceed in forward direction.
• If Qc > Kc, then there are more products present than equilibrium and the reaction will need to produce more reactants shifting the reaction to the left i.e the reaction proceed in backward direction towards reactants.
• If Qc = Kc, then the reaction is already at equilibrium and there will be no shift.

Step 2 : Calculate the Qc

Given,

[SO₃] = 0.50 mol/L

[NO] = 1 mol/L

[SO₂] = 1 mol/L

[NO₂] = 0.50 mol/L

SO₂(g) + NO₂(g) <-----> SO₃(g) + NO(g)

we know, the Q_c expression can be written as

Q_c = [SO₃] × [ NO] / [SO₂] × [NO₂]

on substituting the values

=> Qc = ( 0.50) × ( 1) / ( 1) ×( 0.50  ) = 1   

Step 3 : Compare Qc and Kc
Given,

Kc = 0.33

We got Qc = 1

here, Qc > Kc, So here there are more products present than equilibrium and the reaction will need to produce more reactants shifting the reaction to the left i.e the reaction proceed in backward direction towards reactants and for the equilibrium there will need to be decrease in reaction quotient

So correct option

The reaction will shift in the direction of reactants -----> option(A)

The reaction quotient will decrease.-----> option(C)