Question

1) For the following reaction, Kc = 255 at 1000 K.
CO (g) + Cl2 (g) ⇌ COCl2 (g)
A reaction mixture initially contains a COconcentration of 0.1550 M and a Cl2concentration of 0.175 M at 1000 K.
1a)What is the equilibrium concentration of
CO at 1000 K?
1b)What is the equilibrium concentration of
Cl2 at 1000 K?
c)What is the equilibrium concentration of
COCl2 at 1000 K?
2) At 650 K, the reaction MgCO3(s)⇌MgO(s)+CO2(g) has Kp=0.026. A 12.5 L container at 650 K has 1.0 g of MgO(s) and CO2 at P = 0.0260 atm. The container is then compressed to a volume of 0.500 L .Find the mass of
MgCO3 that is formed.
3) Consider the following reaction:
A(g)⇌2B(g)
Find the equilibrium partial pressures of A and Bfor each of the following different values of Kp. Assume that the initial partial pressure of B in each case is 1.0 atm and that the initial partial pressure of A is 0.0 atm. Make any appropriate simplifying assumptions.
Kp= 1.2
Kp= 2.0×10−4
Kp= 2.0×105

Answer 1

According to the reaction equation:
CO(g) + Cl₂(g) COCl₂(g)

Kc is given as

Kc = [COCl₂] / [CO] [Cl₂] = 255

                          CO(g)       +    Cl₂(g)       COCl₂(g)

Initially                0.1550             0.175                    0

Change               -x                         -x                      x

At equilibrium    0.1550-x             0.175-x                x

Substitute the concentration of reactant at equilibrium into equation of Kc

255 = x / (0.1550-x)(0.175-x)

x = 255 (0.1550-x)(0.175-x)

x = 255 (0.0271 - 0.1550x - 0.175x + x²)

255x² - 85.15x + 6.92 = 0

Solving quadractic equation,

x= 0.1948 or x = 0.139

(x = 0.1948 is infeasible because it would lead to negative concentrations for CO and Cl₂ )

x = 0.139

(a) [CO] = 0.1550-x = 0.016 M

(b) [Cl2] = 0.175-x = 0.036M

(c) [COCl2] = x = 0.139 M