Question

At a certain temperature, the equilibrium constant for the following chemical equation is 2.50.

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

At this temperature, calculate the number of moles of NO2(g) that must be added to 2.86 mol of SO2(g) in order to form 1.30 mol of SO3(g) at equilibrium.

Solve for the number of moles for NO2

Answer 1

Given : Initial Moles of SO2 = 2.86

Let initial moles of NO2 = x

The chemical equilibrium is

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

Initial moles          2.86               x                     0             0

Change                    -y              -y                    +y            +y

Equilibrium        2.86-y              x-y                   y               y
Given : mole sof SO3 at equilibrium = 1.30 so y = 1.30

Now Keq = [SO3][NO] / [SO2][NO2]

2.50 = 1.30 X 1.30 / (2.86-1.30) (x-1.30)

1.48 = 1 / 1.56 X (x-1.30)

(x-1.30) = 0.433

x = 1.733 moles

so number of moles of NO2 that must be added = 1.733 moles