5.1.2: How far?

Question 1

Define mole fraction

Answer 1

A measure of how much of a given substance is present in a reaction mixture relative to other substances at equillibrium

Question 2

Define partial pressure

Answer 2

The pressure an individual gaseous substance would exert if it occupied a whole reaction vessel on its own

Question 3

Are homogeneous equillibria included in the Kc and Kp expression ?

Answer 3

Yes as all reactants and products in same state

Question 4

Are heterogeneous equillibria included in the Kc and Kp expression ?

Answer 4

No only gasses and solids and liquids are omitted as concentrations are constant

Question 5

How do you work out mole fractions ?

Answer 5

Number of moles divided by total number of moles of all gasses

Question 6

What are 2 techniques to determine quantities present at equillibrium ?

Answer 6

• Colorimeter
• Titration (however changing volume will affect equillibrium with the addition of a substance)

Question 7

How do you calculate partial pressure ?

Answer 7

Mole fraction x total pressure

Question 8

What does a decrease in Kp with an increasing temperature show ?

Answer 8

Exothermic forward reaction so equillibrium shifts to the left

Question 9

What happens to Kp if pressure increases ?

Answer 9

The denominator of Kp expression increases more than the numerator so the numerator increases to restore Kp

Question 10

What are units of Kp

Answer 10

atm

Question 11

What happens to Kc if pressure decreases? And what happens to equilibrium mixture ?

Answer 11

Kc doesn’t change with changing pressure but denominator decreases so numerator of Kc expression increases to restore equilibrium

Question 12

What is indicated about a reaction if equilibrium amount of a substance increases at a higher temperature

Answer 12

• Reaction is endothermic as a higher temp caused equilibrium to shift to right and produce higher conc of products
• Equilibrium constant increases as temperature increases indicating endothermic reaction

Question 13

What happens to Kp if equillibrium shifts in the endothermic direction ?

Answer 13

It decreases

Question 14

What happens to Kp if equillibrium shifts in the exothermic direction?

Answer 14

It increases

Question 15

What is the effects on changing pressure and adding a catalyst to Kp ?

Answer 15

No effect ( catalysts only speed up rate of forward and reverse reaction)

Question 16

How is Kc affected if equillibrium shifts in the endothermic direction ?

Answer 16

Kc decreases

Question 17

How is Kc affected if equillibrium shifts in the exothermic reaction?

Answer 17

Kc increases

Question 18

What 2 factors have no effect on Kc ?

Answer 18

Catalysts and concentration