Exactly 3.0 mol NO and 2.0 mol O2 were placed
in a 1.00-L flask. These gases react as follows:
2 NO + O2 2 NO2 .
At equilibrium, the mixture contained 2.0 mol
NO2. What is the Kc for the reaction above?
A 0.50
B 1.00
C 2.0
D 2.5
E 4.0
I'm confused how to get this answer
This is my ice chart
2NO + O2 = 2NO2
I 3 2 -
C 2x x x
E 3+2x 2+x x
you used 1 mole NO, used .5 mole O2, and created 1 mole NO2
Kc=1^2 /(1^2*.5)= 2.0
how is .5 of o2 used?
To find the equilibrium constant (Kc) for the given reaction, we need to use the concentrations of the reactants and products at equilibrium.
First, let's find the initial concentrations of NO, O2, and NO2. The problem states that exactly 3.0 mol NO and 2.0 mol O2 were placed in the 1.00-L flask. Therefore, the initial concentration of NO is:
[NO]initial = (3.0 mol) / (1.00 L) = 3.0 M
Similarly, the initial concentration of O2 is:
[O2]initial = (2.0 mol) / (1.00 L) = 2.0 M
Since there were no NO2 at the beginning, the initial concentration of NO2 is:
[NO2]initial = 0 M
Now, let's look at the equilibrium concentration of NO2, which is given as 2.0 mol. The equilibrium concentration of NO2 is:
[NO2]equilibrium = 2.0 M
According to the balanced equation, the stoichiometry of the reaction is 2:1:2 for NO:O2:NO2. Therefore, at equilibrium, the concentration of NO should be half of the concentration of NO2 since two moles of NO2 are produced from two moles of NO. Thus:
[NO]equilibrium = (1/2) * [NO2]equilibrium = (1/2) * (2.0 M) = 1.0 M
The equilibrium concentration of O2 can be found by subtracting the concentration of NO2 produced from the original concentration of O2. Since the stoichiometry is 2:1 for O2:NO2:
[O2]equilibrium = [O2]initial - [NO2]equilibrium = 2.0 M - 2.0 M = 0 M
Now, we can write the equilibrium expression using the equilibrium concentrations we found:
Kc = ([NO2]equilibrium) / ([NO]equilibrium)^2 * ([O2]equilibrium)
Plugging in the values:
Kc = (2.0 M) / (1.0 M)^2 * (0 M)
Kc = 2.0 / 1.0 * 0
Since any number divided by zero is undefined, the equilibrium constant Kc for this reaction is undefined. Therefore, none of the answer choices (A through E) are correct.