Question

Consider the reaction CO(g)+NH3(g)⇌HCONH2(g), Kc=0.870 If a reaction vessel initially contains only CO and NH3 at concentrations of 1.00 M and 2.00 M, respectively, what will the concentration of HCONH2 be at equilibrium?

Answer 1

Solution-

Given- Kc = 0.870

Initial concentration of CO = 1.0 M

Initial concentration of NH3 = 2.0 M

Let’s write the given reaction

CO(g) + NH3(g) ⇌ HCONH2(g)

Let’s set up the the ICE chart for the reaction

                CO(g)        +       NH3(g)     à       HCONH2(g)

I               1.0 M            2.0 M                       0                     

C            -x                    -x                          + x                    

E         (1.0-x)             (2.0-x)                    x         

Equilibrium constant for reaction is

Kc = [HCONH2]/[CO][NH3] = x/(1.0-x)(2.0-x)

0.87 = x/(1-x)(2-x)

(1.0 - X) x (2.0 - X) = X/0.870

2.0 - 3.00 X + X^2 = 1.15 X

X^2 - 4.15x + 2.0 = 0
Using the quadratic formula,

we get two answers,

x = 0.55 M and x = 3.59 M.

Since [CO] cannot lose more than 1.00 M in concentration,

Therefore [HCONH2] = [ x] = 0.55 M.

Answer- concentration of HCONH2 be at equilibrium = 0.55 M.