C(s) + 2 H2(g) = CH,(9) has Kp = 0.263 at 1000. K. Calculate the total pressure at equilibrium when 5.207 g of H, and 23.29 g of C(s) are placed in
a 9.32 L flask and heated to 1000, K.
atm
Protal =

Calculate the total pressure when 5.207 g of H, and 8.333 g of C(s) are placed in a 9.32 L flask and heated to 1000. K.
atm
Ptotal =

Total pressure for both systems is 14.26atm.

Explanation:

Kp for the reaction is:

As C is a pure solid, is not taken into account for Kp expression.

5.207g of H₂ are:

5.207g ₓ (1 mol / 2.01g) = 2.59moles of gas.

Using PV = nRT:

P = 2.59molₓ0.082atmL/molKₓ1000K / 9.32L = 22.8atm

The expressions for pressure in equilibrium are:

P{H₂} = 22.8atm - 2X

P{CH₄} = X

Replacing in Kp expression:

0.263 = X / (22.8 - 2X)²

0.263 = X / 520 - 91.2X +4X²

136.8 - 24X + 1.052X² = X

Solving for X:

X = 8.54atm → Right solution

X = 15.22atm → False solution. Because produce a negative concentration.

Replacing:

P{H₂} = 22.8atm - 2*8.54atm = 5.72atm

P{CH₄} = 8.54atm

Pressure of H₂ is 5.72atm and pressure of CH₄ is 8.54atm. Total pressure is:

5.72atm + 8.54atm = 14.26atm

As mass of Carbon is not taken into account is Kp expression and mass of hydrogen is the same with the same volume, total pressure is also 14.26atm