# The equilibrium constant Kc for the reaction below is is 5.555×10-5 . C<--->D+E The initial composition of the reaction mixture is [C] = [D] = [E] = 1.9110×10-3 M. What is the equilibrium concentration for C, D, and E?

##### 1 Answer

The equilibrium concentrations are

#### Explanation:

At equilibrium,

**Equation 1**

Let x = the extent of reaction at equilibrium. At constant volume, we can make

[

Let's define

At equilibrium

[

[

[

Substituting these three equations into **Equation 1** gives

Multiply both sides by

Putting this in standard form gives

Solve for

Note that this is an equilibrium reaction, so x can be negative as well as positive, but its absolute value cannot be more than

This simplifies to

Lets try the other value

This simplifies to

So the equilibrium concentrations are

Note we can check our answer

which is the equilibrium constant given in the problem statement.