CHEMISTRY HELP Consider the reaction. A(aq)↽−−⇀2B(aq) KC=7.81×10^−6 at 500 K

Question

Consider the reaction.

A(aq)↽−−⇀2B(aq)𝐾c=7.81×10−6 at 500 K



If a 5.40 M sample of A is heated to 500 K, what is the concentration of B at equilibrium?

Answer 1

Volume isn't changing so let's use the change in the molarity of A towards equilibrium (call it x) as a measure of the extent of forward reaction.

[A]_eq = 5.4 - x

[B]_eq= 2x

K expression at equilibrium is [B]²/[A] = 7.81x10^-6 (at equilibrium)

You can plug in the values and solve the quadratic equation in x.

However, you can make the assumption that x is small compared to 5.4 (check for 5% rule later)

The equation becomes 4x²/5.4 = 7.81x10^-6 (which will prove more than adequate)