Question

Suppose a 500.mL flask is filled with 1.0mol of CO, 1.5mol of H2O and 0.70mol of CO2. The following reaction becomes possible: +COgH2Og +CO2gH2g The equilibrium constant K for this reaction is 3.80 at the temperature of the flask. Calculate the equilibrium molarity of CO. Round your answer to two decimal places.

Answer 1

Answer:

[CO] = 0.62 M

Explanation:

Step 1: Data given

Volume of the flask = 500 mL

Number of moles CO = 1.0 moles

Number of moles H2O = 1.5 moles

Number of moles CO2 = 0.70 moles

The equilibrium constant K for this reaction is 3.80

Step 2: The balanced equation

CO(g) + H2O(g) ⇆ CO2(g) +H2(g)

Step 3: Calculate the initial concentrations

Concentration = moles / volume

[CO] = 1.0 moles / 0.500 L = 2.0 M

[H2O] = 1.5 moles / 0.500 L = 3.0 M

[CO2] = 0.70 moles / 0.500 L = 1.4 M

[H2] = 0M

Step 4: The concentration at the equilibrium

For 1 mol CO we have 1 mol H2O to produce 1 mol CO2 and 1 mol H2

[CO] = 2.0 -X M

[H2O] =  3.0 - X M

[CO2] =1.4 + X M

[H2] = X M

Step 5: Define Kc

Kc = [CO2][H2]/ [CO][H2O]

3.80 = (1.4 + X) * X / ((2.0 - X)*3.0 -X))

X = 1.38

[CO] = 2.0 -1.38 = 0.62 M

[H2O] =  3.0 - 1.38 = 1.62 M

[CO2] =1.4 + 1.38 M = 2.78

[H2] = 1.38 M

Kc = (2.78*1.38) / (0.62*1.62)

Kc = 3.8

[CO] = 0.62 M