Question

At a certain temperature, the equilibrium constant for the following chemical equation is 3.40. SO2(g)+NO2(g)----> SO3(g)+NO(g)

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At this temperature, calculate the number of moles of NO2(g) that must be added to 2.42 mol of SO2(g) in order to form 1.10 mol of SO3(g) at equilibrium.

Answer 1

let the mol of NO2 added be n
SO2(g)       +   NO2(g)   <——>   SO3(g)   +   NO(g)
2.42           n               0           0       (initial)
2.42-x           n-x               x           x       (at equilibrium)

At equilibrium:
mol od SO3 = x = 1.10 mol

Kc = [SO3][NO]/[SO2][NO2]
3.40 = x*x / ((2.42-x)(n-x))
3.40 = 1.10*1.10 / ((2.42-1.10)(n-1.10))
3.40 = 1.21 / (1.32(n-1.10))
3.40 = 1.21 / (1.32*n-1.452)
4.488*n - 4.94 = 1.21
4.488*n = 6.15
n = 1.37 mol

Answer: 1.37 mol