Topic 11 - Further Equilibrium

Question 1

What is a homogenous reaction?

What is a heterogeneous reaction?

Answer 1

Homogenous - one in which all reactants and products are in the same phase e.g. All gases or all aqueous
Heterogeneous - one in which at least one of the reactants and or products is in a different phase to the others - when writing Kc only use gas

Question 2

What factor affects the value of the equilibrium constant?

Answer 2

Temperature

Question 3

What is partial pressure?

Answer 3

Partial pressure of a gas in a mixture of gases is the pressure that the gas would exert if it alone occupied the volume of the mixture

Question 4

How to calculate the partial pressure of an individual gas in a mixture of gases

Answer 4

Pa = mole fraction X total pressure

Mole fraction = number of moles of A / total moles of gas

Question 5

Kp for homogenous and heterogenous reactions

Answer 5

Total pressure of a mixture is equal to the sum of the partial pressures of all the gases
Kp = pCO2(g)

Question 6

Describe effect of temperature on Kp and Kc e.g. Exothermic reaction between N2, H2 and NH3
Endothermic reaction too

Answer 6

Value of Kp decreases with the increasing temperature - same for Kc
Exothermic - increase temperature -K decreases
Exothermic - decrease temperature - K increases
Endothermic - increase Temperature - K increases
Endothermic - decrease temperature - K decreases

Question 7

How does the change in temperature alter the equilibrium position

Answer 7

If equilibrium constant for a reaction changes with a change in Temperature then it follows that the equilibrium position also changes
E.g. H2 + I2 –> 2HI
As value of Kp decreases as temp increases, the % of H2 and I2 increases and the % of HI increases - equilibrium shifts to the left in the endothermic direction as temp increases

Question 8

Describe effect of concentration of equilibrium constant

Answer 8

Position changes when concentration is altered
On factor that changes value of Kc is temperature - the reaction quotient Qc changes when conc is altered so no longer equal to the Kc so equilibrium composition changes until the reaction quotient and equilibrium constant are equal
So at equilibrium Qc = Kc