Question

1.) Consider the equilibrium N2(g) +3H2(g) = 2NH3

for which Kc = 6.00 x 10-2 at 500 C

a.) do reactants or products predominate in an equilibrium mixture at 500 C

b.) An equilibrium mixture was found to have the following concentrations [H2] = .250 M [NH3] = 5.00 x 10-7 M at 500 C. What is the [N2] at equilibrium?

c.) What is the numerical value of Kp at 500 C

Answer 1

a)

Kc is defined as concentration of product by concentration of reactant with each concentration term raised to power that is equal to its stoichiometric coefficient in balanced equation

Since Kc is less than 1, reactants will dominate

Answer: reactants

b)

Kc = [NH3]^2 / [N2][H2]^3

6.00*10^-2 = (5.00*10^-7)^2 / [N2](0.250)^3

[N2] = 2.67*10^-10 M

Answer: 2.67*10^-10 M

c)

T= 500.0 oC

= (500.0+273) K

= 773 K

Δ n = number of gaseous molecule in product - number of gaseous molecule in reactant

Δ n = -2

use:

Kp= Kc (RT)^Δ n

Kp = 6*10^-2*(0.08206*773.0)^(-2)

Kp = 1.491*10^-5

Answer: 1.49*10^-5