Question

Hi!

I kep trying this question and can't get it right.

At a certain temperature, the equilibrium constant for the following chemical equation is 2.90. At this temperature, calculate the number of moles of NO2(g) that must be added to 2.73 mol of SO2(g) in order to form 1.30 mol of SO3(g) at equilibrium.

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

Answer in mol NO2

Answer 1

Let number of moles of NO2 to be added be x

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

initial:                                    2.73          x                0              0

At equilibrium:                    2.73-y         x-y              y               y

Given in question that: number of mol of SO3 at equilibrium = 1.3 mol

so, y = 1.3 mol

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

initial:                                    2.73          x                0              0

At equilibrium:                    2.73-1.3        x-1.3            1.3               1.3

At equilibrium:                     1.43        x-1.3            1.3               1.3

Kc= [SO3][NO] /{[SO2][NO2]}

2.9 = 1.3*1.3 / (1.43 *(x-1.3))

x-1.3 = 0.41

x = 1.71 mol

Answer: Number of moles of NO2 added = 1.71 mol