Question

a) In order to study hydrogen halide decomposition, a researcher fills an evacuated 1.79 L flask with 0.452 mol of HI gas and allows the reaction to proceed at 428°C: 2HI (g)  ⇋  H₂(g) + I₂(g)

At equilibrium, the concentration of HI = 0.055 M. Calculate K_c. Enter to 4 decimal places.

HINT: Look at sample problem 17.6 in the 8th ed Silberberg book. Write a K_c expression. Find the initial concentration. Fill in the ICE chart. Put the E (equilibrium) values into the K_c expression.

b)

In a study of the conversion of methane to other fuels, a chemical engineer mixes gaseous methane and gaseous water in a 0.332 L flask at 1,085 K. At equilibrium, the flask contains 0.206 mol of CO gas, 0.109 mol of H₂ gas, and 0.134 mol of methane. What is the water concentration at equilibrium (Kc = 0.30 for this process at 1,085 K)?

Enter to 4 decimal places.

HINT: Look at sample problem 17.7 in the 8th ed Silberberg book. Write a balanced chemical equation. Write the K_c expression. Calculate the equilibrium concentrations of all the species given (moles/liter). Put values into K_c expression, solve for the unknown.

c)

Look at sample problem 17.10 in the 8th edition Silberberg book.

The research and development unit of a chemical company is studying the reaction of methane and H₂S, two components of natural gas:

CH₄ (g) + 2 H₂S (g)  ⇋   CS₂ (g) + 4 H₂ (g)

In one experiment, 1.5 mol of CH₄, 1.5 mol of CS₂, 2.5 mol of H₂S, and 2.5 mol of H₂ are mixed in a 200. ml vessel at 960°C. At this temperature, Kc = 0.064.

In which direction will the reaction proceed to reach equilibrium? Enter right, left, at equilibrium,

If the concentration of methane at equilibrium is 10.0 M, what is the equilibrium concentration of H₂? Enter a number to 1 decimal place.

Answer 1

a) Initial concentration of [HI] = 0.452mol/1.79 L = 0.2525 M

Hence use ICE table:

c) Reaction quotient Qc is similar to Kc, except the concentrations are expressed at the initial stage before reaching the equilibrium.
if Kc < Qc then the reaction will favor the reactants i.e. left.
if Kc > Qc then the reaction will favor the products i.e. right.
if Kc = Qc then it is at equilibrium.