10 Points Best Answer Chemistry Help?

Question

Ok, I know I just asked a question about chemistry help. But I didn't realize that I had this question also. I'm just really confused about the whole equilibrium process and how to solve it. (My teacher is horrible). Could you explain how you got the answer and the steps you took to get there. Thanks so much! (Best answer = 10 points!) 

Given the equilibrium:


2 A2(g) --> B(g)+ C (g)

the equilibrium concentrations of A2(g), B(g) and C(g) were found to be 0.62M; 0.79M and 0.79M. An additional amount of A2 was added to the flask such that the concentration of A2(g) rose to 2.67M, then equilibrium was re-established. Calculate the new equilibrium concentration of B(g). Enter the result with 3 significant figures.

Real Chemist · Accepted Answer

2 A2 (g) ----> B (g)+ C (g)

Equilibrium Constant = [ B ] x [ C ] / [ A2 ]^2

At the first Equilibrium 
Equilibrium Constant 
= [ 0.79 ] x [ 0.79 ] / [ 0.62 x 0.62]
= 1.6235691 

After addition of A2 [ such that the concentration of A2(g) rose to 2.67M ] and Equilibrium re-established . . . .

If concentration of B change to 0.79 + d 
Concentration of C will also change to 0.79 + d 
Concentration of A2 will change to 2.67 - 2d 

At the Second Equilibrium 

Equilibrium Constant 
= [ 0.79 = d ] x [ 0.79 + d ] / [ ( 2.67 - 2d ) x ( 2.67 - 2d ) ]

1.6235691 = [ 0.79 = d ] x [ 0.79 + d ] / [ ( 2.67 - 2d ) x ( 2.67 - 2d ) ]

d = 0.736136 

Concentration of B ( at new equilibrium ) = 0.79 + 0.736136 
= 1.526136 M

Your answer should be 
Concentration of B ( at new equilibrium ) = 1.53 M 


Note : 
Don't just blame your teacher . If you carefully read your book ( to understand chemical equilibrium and related principles ) , carefully read the question , use some common senses >> you will be able to do it by yourself .

Anonymous · Answer

It appears to me that there are some issues with the question. "2 A2(g) --> B(g)+ C (g)" Is this equation suppose to be balanced? Also the way its written "2 A2" makes it look like A is becoming B and C rather than just breaking into B and C which is a very fundamental problem. 

I'm going to say the best I can do is guess so if someone else could back up my work as right or wrong that would help

Take the [concentration] of products over reactants = [B][C]/[A2]^2

plug in the numbers and set that equal to [B][C]/[A2]^2 with the new numbers.

.79^2/.62^2 = 1.6235

1.6235 = X^2/2.67^2 --> x^2 = (1.6235)(2.67^2) --> x = 3.40 M B

Hope that helps, I skipped some math steps as implied.

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10 Points Best Answer Chemistry Help?

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