Answer:
Kc = 0.7731
Explanation:
Let's write the given reaction:
2NO2 <-------> NO + O2
Now, we know that initially we have 8 mol of NO2, at 1 L (Concentration is 8 M then). At the end of the equilibrium we have letf 2.9 M of NO2 and we need to calculate the value of K, which is the equilibrium constant.
Now, the expression to calculate equilibrium constant is:
Kc = [Product]/[Reactants]
Aplying this to the given reaction we have:
Kc = [NO] [O2] / [NO2]²
But these concentrations must be in equilibrium. To know this, we use an ICE chart in this reaction, and see what we have:
2NO2 <-------> NO + O2
I: 8 0 0
C: -2x +x +x
E: 8 - 2x x x
According to this, we know that the concentration in equilibrium of NO2 is 8 - 2x; however we know that the total of this is 2.9, so we can solve for x from here:
2.9 = 8 - 2x
2x = 8 - 2.9
2x = 5.1
x = 5.1/2
x = 2.55 mol/L
This means that the concentrations in equilibrium of NO and O2 are 2.55, so the equilibrium constant Kc would be:
Kc = 2.55 * 2.55 / (2.9)²
Kc = 0.7731
And this is the value of Kc.