5.60 g of solid carbon is placed in a rigid evacuated 2.5 L container. Carbon dioxide is added to th — Equilibrium Chemistry Question
Problem Context
5.60 g of solid carbon is placed in a rigid evacuated 2.5 L container. Carbon dioxide is added to the container to a final pressure of 1.50 atm at 298 K.
Calculate the number of moles of each reactant in the container originally.
Model Answer
n = 0.153 mol
The container is heated to 1100 K and the following reaction occurs:
C(s) + CO2(g) ⇌ 2 CO(g) ∆H˚ = 173 kJ
i. Calculate the pressure in the container at this temperature before the reaction takes place.
Model Answer
P2 = 5.54 atm
ii. When equilibrium is reached the pressure inside the container is 1.75 times that calculated in b.i. Determine the equilibrium partial pressures of CO2(g) and CO(g).
Model Answer
PCO = 8.31 atm
iii. Write the equilibrium expression for this reaction, Kp.
iv. Calculate the value of Kp for this reaction at 1100 K.
Model Answer
Kp = 4.50
Predict the effect on the number of moles of carbon monoxide of each of the following changes made to this system at equilibrium. Give reasons for your predictions.
i. The volume of the container is increased to 5.0 L.
Model Answer
nCO will increase. As V is ↑, P ↓ so system shifts →.
ii. The pressure inside the container is increased by adding helium.
Model Answer
nCO does not change. He is not in Kp so has no effect.
iii. The temperature of the system is increased to 1200 K.
Model Answer
nCO will increase. ΔΗ is positive so T ↑ will favor →.
iv. The amount of solid carbon is increased to 6.00 g.
Model Answer
nCO will not change. Solids do not affect equilibrium.