Question

Part B

What is the final concentration of Dat equilibrium if the initial concentrations are [A] = 1.00 mol L−1 and [B] = 2.00 mol L−1 ?

Express your answer to two significant figures and include the appropriate units.

The reversible chemical reaction

A(aq)+B(aq)⇌C(aq)+D(aq)

has the following equilibrium constant:

K=[C][D][A][B]=2.5

Part A

Initially, only A and B are present, each at 2.00 mol L−1. What is the final concentration of A once equilibrium is reached?

Express your answer to two significant figures and include the appropriate units.

Answer 1

You have

Part A

You have

From the reaction, you can see that at equilibrium C and D have the same concentration (because they have the same stoichiometric coefficient), and the concetration of B and A should be less the initial, and still the same concentration. So at equilibrium:

The K estabilshes the ration at equilibrium of all the species in the reaction. using the equation for K you can calculate X:

This yields an equation as follows:

and can be solve with the quadratic equation:

X=1.225M

so A at equilibrium is 2-1.225=0.775mol/L

Part B

As in part A, the only difference is that A and B are not equal:

Intial

Equilibrium

At equilibirum

This yields an equation as follows:

and can be solve with the quadratic equation:

X=0.792mol/L=D