Question

4. At a given temperature, the equilibrium constant Kc for the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g) is 3.0x10^9 . If 1.00 mol of SO2 and 2.00 mol of O2 are placed in a 1.00 L container and allowed to react to equilibrium at this temperature, what is the concentration of SO3 at equilibrium?

a) 0.500 M

b) 1.00 M

c) 2.00 M

d) 3.87 x10^4 M

e) none of these

Answer 1

Since Kc is large, this is not an equilibrium question.

The reaction can be assumed to be complete.

Balanced chemical equation is:

2 SO2 + O2 ---> 2 SO3 +

2 mol of SO2 reacts with 1 mol of O2

for 1 mol of SO2, 0.5 mol of O2 is required

But we have 2 mol of O2

so, SO2 is limiting reagent

we will use SO2 in further calculation

According to balanced equation

mol of SO3 formed = (2/2)* moles of SO2

= (2/2)*1

= 1 mol

[SO3] = mol of SO3 / volume in L

= 1 mol / 1.00 L

= 1.00 M

Answer: b