Equilibrium

Question 1

What is homogenous equilibria

Answer 1

contains equilibrium species that all have the same state/phase.

Question 2

What is heterogenous equilibrium

Answer 2

contains equilibrium species that have different states or phases

Question 3

What species are included in the kc equation

Answer 3

g or aq

Question 4

Describe an experiment to determine kc

Answer 4

1. In a conical flask mix 0.1 mol of CH3COOH and 0.1 mol of C2H5OH and 0.005 mol of HCl. The total volume is 20 cm3. Amount of water in acid catalyst is 0.5 mol.
2. add 0.005 mol of HCl to a second flask as a control.
3. stopper both flasks and leave for a week to reach equilibrium.
4. carry out a titration on the equilibrium mixture using a standard solution of NaOH.
5. Repeat the titration with the control to determine the amount of acid catalyst that has been added.

Question 5

How could you analyze the results of the kc practical

Answer 5

Using the 2 titrations determine the amount of CH3COOH and then use this to determine equilibrium concentrations of each component. Work out concentrations and substitute them into the kc equation to find a value for kc

Question 6

What is the mole fraction of a gas

Answer 6

its proportion by volume to the total volume of gases in a gas mixture

Question 7

mole fraction formula

Answer 7

mole fraction x(A) = number of moles of A/total number of moles in a gas mixture

Question 8

What is partial pressure

Answer 8

the contribution that the gas makes towards the total pressure

Question 9

Partial pressure formula

Answer 9

mole fraction of A x total pressure

Question 10

Write kp for equilibrium of H2 + I2 -> 2HI

Answer 10

p(HI)^2/(p(H2) x p(I2))

Question 11

What species does kp include

Answer 11

Gases only

Question 12

What does k tell you

Answer 12

the exact position of equilibrium e.g. if k = 2 then equilibrium is product favored

Question 13

What can change the value of k

Answer 13

Temperature

Question 14

If you increase the temperature, how does k change with a forward exothermic reaction?

Answer 14

equilibrium constant decreases with increasing temperature. The equilibrium yield of products decreases.

Question 15

Explain the effect on k that increasing temperature has in an exothermic reaction

Answer 15

k decreases because partial pressure of the products decreases, and the partial pressure of the reactants increases so equilibrium position is more towards the left.

Question 16

What is the effect on k does increasing the temperature have on a forward endothermic reaction?

Answer 16

Equilibrium constant increases with increasing temperature, and increases the equilibrium yield of products

Question 17

Explain the effect on k with increasing temperature in endothermic reaction

Answer 17

k increases, partial pressure of product increases, partial product of reactants decrease so equilibrium shifts right