Module 3 #19

[Haley Dveirin 1E]

Can someone explain how to solve this and what the answer is:

0.482 mol N2 and 0.933 mol O2 are placed in a 10.0 L reaction vessel and form N2O (dinitrogen oxide): 2N2(g) + O2(g) ⇌ 2N2O(g) KC = 2.0 x 10-37 
What is the composition of the equilibrium mixture?

[Brooke Yasuda 2J]

So the moles of the reactants are given and the volume is also given. With this, you can calculate the concentration of N2 and O2. Then, you set up an equilibrium ICE table. When you do the "change" part of ICE, remember to look at the molar ratios of the reactants and products. Then, calculate the equilibrium constant and equate it to 2.0 x 10^-37. From here you can solve for the change x and find the equilibrium concentrations of the reactants and products.

[faithkim1L]

First, convert moles given to molarity. It's a 10.0 L container, so the molarities of N2 and O2 are .0482 and .0933 respectively.

With the equation given, Kc = [NO2]^2/[O2][N2]^2

Create the ICE table.
N2 O2 N2O
I .0482 .0933 0
C -2x -x 2x
E .0482 - 2x .0933 - x 2x

Kc = 2.0 x 10^-37
Kc = (2x)^2/(.933 - x)(.482 - 2x)^2

*Since Kc is so small, we can assume that at equilibrium, there is a large amount of reactant and a very small amount of product. We can assume that the value of x makes an inconsequential different in the initial molarities of the reactants, so we can just treat "x" as 0.

Kc = 4x^2/(.933)(.482)^2
x = 3.3x10^-21

Use this x value and plug it into the equilibrium molarities.