Equilibrium Constant

Question 1

In an exam question, you’re told that 2 given reactants were mixed in a given mole ratio and left to reach equilibrium in a flask at a given temperature. You’re also given the balanced equation for the reversible reaction. When equilibrium was reached, the total pressure in the flask is given and the mole fraction of the sole product in the mixture is given. How do you find the partial pressure of each gas in the equilibrium mixture?

Answer 1

1. Because mole fraction of the only product is given, the mole fraction of the sum of the 2 reactants is 1 minus Mole Fraction Given
2. Molar ratio of the 2 reactants is given and can be used as well as the value just calculated to find the molar fraction of each reactant (sum of ratio = calculated mole fraction; e.g. if ratio is 3:2 for A & B respectively where they are 2 reactants, 5x = calculated mole fraction from step 1, rearrange to find x, 2x = mole fraction of B, 3x = mole fraction of A)
3. Find partial pressure of each substance by doing mole fraction multiplied by total pressure given

Question 2

If reaction has an equation A + 2B <-> 3C + D, give the Kp equation

Answer 2

Kp = (pp C)^3 x (pp D) over (pp A) x (pp B)^2

Question 3

What’s a homogeneous system?

Answer 3

A homogeneous system in equilibrium is one where all its components are of the same phase

Question 4

What’s the name for a ‘system in equilibrium is one where all its components are of the same phase’?

Answer 4

A homogeneous system

Question 5

In a question, you’re given a gaseous reversible reaction where there is one mole of a reactant and one mole of 2 products. You’re given the partial pressure of one of the products and total pressure of the reaction. How would you find the partial pressure of the reactant?

Answer 5

1. total pressure given = partial pressure of product given + partial pressure of product given (again because there are the same number of moles of each of the 2 products so they’d have the same partial pressure) + pp(symbol of reactant)
2. Rearrange equation to find pp(symbol of reactant*)

Question 6

What’s the equation for the Contact Process?

Answer 6

2SO2 (g) + O2 (g) ↔ 2SO3 (g)

Question 7

What’s Kp for Heterogeneous systems?

Answer 7

Kp for heterogeneous systems are the same as for homogeneous systems, except non-gas species are not part of the equation

Question 8

Give the Kp equation for the following reversible reaction: A (g) + 2B (g) <=> 5C (s)

Answer 8

Kp = 1 / ppA x (ppB)^2

Question 9

What is partial pressure?

Answer 9

Each gas’ contribution to the total pressure

Question 10

What is the mole fraction?

Answer 10

Number of moles of gas X in the mixture over total number of moles of gas in the mixture