The concentration of B at equilibrium

[JessicaHelena]

Homework Statement

For the reaction given below, 2.00 moles of A and 3.00 moles of B are placed in a 6.00L container.
A(g) + 2B(g) --> C(g)
At equilibrium, the concentration of A is 0.246 mol/L. What is the concentration of B at equilibrium?

Homework Equations

for aA+bB-->cC,
K = [C]^c/([A]^a[ B]^b)

c=n/V

The Attempt at a Solution

Frankly, I'm not sure what to do here. The LR is B since using all 3.00 moles of B, we'd only need 1.5 moles of A, but that's when the reaction goes to completion and we don't know if it does. Also, we are not given C's concentration or the K value... What can I do here?

 

[DrClaude]

The LR is B since using all 3.00 moles of B, we'd only need 1.5 moles of A, but that's when the reaction goes to completion and we don't know if it does.

That's something you can figure out

Also, we are not given C's concentration or the K value...

It is not given because it is not needed.

What can I do here?

What happens to A and B when you mix them? What is the relation between the concentrations of A, B and C?

 

[JessicaHelena]

how can I figure at which point the experiment stops — I'm still not so sure.

The amount of A and B decrease to produce C.

concentrations of A:B:C = # of moles of A:B:C

 

[Borek]

Think in terms of a simple stoichiometry.

 

[JessicaHelena]

So then at equilibrium, there'd be 0.246 mol/L of A, and 0.246 x 2 mol/L of B and 0.246 mol/L of C?

 

[mjc123]

No. you have the concentration of A, and the volume. How many moles of A are there?
So how many moles of A have reacted?
How many moles of B have reacted, and how many are left?
What is the concentration of B?
Have you heard of an ICE table?