Chemistry Help Please!

Question

The reversible chemical reaction: A+B<->C+D has the following equilibrium constant: Kc=[C][D]/[A][B]=4.1.

 

(a) Initially, only A and B are present, each at 2.00 M. What is the final concentration of A once equilibrium is reached?

 

(b) What is the final concentration of D at equilibrium if the initial concentrations are [A]=1.00M and [B]=2.00M?

Answer 1

(a)

Set up an ICE table.

 

                 A      +      B      →      C   +      D

 

Initial         2.00         2.00

Change         -x            -x           +x          +x

Equil          2.00-x       2.00-x        x            x

 

Then K = 4.1 = x² / (2.00 - x)²

 

You can solve this one by taking the square root of each side.

 

2.02 = (4.1)^1/2 = x / (2.00 - x)

 

Then solve for x.   [A] = 2.00 - x

 

 

(b) 

Basically this one is the same, except for the starting amounts, and you need to use the quadratic formula to solve for x.  Then, [D] = x.