[attachment id=0 msg=3646] I got this wrong, but I am not sure why. I got the same answer as the explanation says for x, but don't you have to multiply 2 to get [C] since there is a 2 in front of it?

K = 4*10^(-6) = (2x)^2/(0,1-x)^2
0,002 = 2x/(0,1-x)
0,0002- 0,002x = 2x
0,0002 = 2,002x
x = 0,00000999 ~ 1*10^(-4)
b is correct answer

Mistake
K = 4*10^(-6) = (x)^2/(0,1-x)^2
0,002 = x/(0,1-x)
0,0002- 0,002x = x
0,0002 = 1,002x
x = 0,0001996 ~ 2*10^(-4)
a is correct answer

Quote from: ann on March 03, 2023, 01:25:52 PM
[attachment id=0 msg=3646] I got this wrong, but I am not sure why. I got the same answer as the explanation says for x, but don't you have to multiply 2 to get [C] since there is a 2 in front of it?

Hi You are right .
[C] = 2x = 2* 2* 10^-4
Excellent Ann!

So all given solutions are wrong. Correct would be 4 x 10^-4 M what is not in the list?
And what would be correct for

A + B => 2C

K = C^2/(A?B) or K = (2*C)^2/(AxB)

Option a is correct


Plug in the concentration and calculate X
X = (K * (0.1)(0.1)/4)^(1/2) = 1.0 * 10^-4 M
[C] = 2x = 2.0 * 10^-4 M
I think student did some error in calculating x value but she is right that it is 2x . So answer a is the right answer.

QuoteK = (2*C)^2/(AxB)

is wrong expression.