1.7 Equilibira And Acid Base Reactions

Question 1

Define a reversible reaction

Answer 1

A reaction in which the conversion of reactants to products and conversion of products to reactants occurs simultaneously

Question 2

Define dynamic equilibrium

Answer 2

Equilibrium that occurs in a closed system when the rate of forward is equal to the rate of reverse reaction

Question 3

Define Le Chateliers principle

Answer 3

States that when a system in dynamic equilibrium is subjected to a change, the position of equilibrium will shift to minimise the change

Question 4

3 ways to shift equilibrium

Answer 4

• concentration
• pressure
• temperature

Question 5

How does increased concentration impact equilibrium and yield?

Answer 5

If the concentration of [ions/chemical] is increased the equilibrium will shift to oppose this and move in the forward direction to remove and decrease the concentration of [ions/chemical] therefore increasing the yield of [products]
—> favour forward reaction

Question 6

How does an increase in pressure affect equilibrium?

Answer 6

An increase in pressure will favour the side of the reaction with the least amount of gaseous molecules as this will reduce pressure in the system

Question 7

How does increased pressure affect equilibrium and yield?

Answer 7

If pressure is increased the equilibrium will shift to oppose this and move in the forward direction as this is where there are the fewest moles of gas to try and reduce the pressure. This will then increase the yield of [product]

Question 8

How does temp impact equilibrium?

Answer 8

• an increase in temp of an exothermic reaction will favour the endothermic reaction as this will reduce the temp of the system, so equilibrium shifts to left.
• a decrease in temp of an exothermic reaction will favour the exothermic reaction as this will increase the temp of the system, so equilibrium shifts right
• increase in temperature of an endothermic reaction will favour the endothermic reaction, so shift right
• decrease in temperature of an exothermic reaction will favour the exothermic so shift left

Question 9

Impact of a catalyst on equilibrium

Answer 9

No affect

Question 10

Kc

Answer 10

Equilibria constant

Question 11

Kc equation

Answer 11

• product / reactant
• conc to power of stoichiometric values

Question 12

What happens when Kc»1

Answer 12

• forward reaction favoured
• equilibrium lies to the right

Question 13

What happens when Kc«1?

Answer 13

• favours backward reaction
• equilibrium to left

Question 14

What happens when Kc=1?

Answer 14

Reactants and products are equal

Question 15

Define an acid

Answer 15

Proton donator

Question 16

Define a base

Answer 16

Proton acceptor

Question 17

Define an alkali

Answer 17

• soluble base (dissolves in water to form OH- ions)

Question 18

What does pH measure?

Answer 18

H+ ion concentration

Question 19

What is the concentration of H+ ions in a monoprotic strong acid?

Answer 19

The same as the conc of the acid as strong acids completely dissociate

Question 20

What is the conc of H+ ions in a diprotic acid?

Answer 20

Double the conc of the acid

Question 21

What is the acid dissociation constant?

Answer 21

Ka

Question 22

What does a large Ka value mean?

Answer 22

Larger Ka = larger extent of dissociation and therefore stronger acid

Question 23

What does a small Ka value mean?

Answer 23

Smaller Ka = smaller extent of dissociation therefore weaker acid

Question 24

pH equation

Answer 24

-log(H+)

Question 25

H+ equation

Answer 25

10^-pH

Question 26

Graph shows % product decrease as temp increase. Explain whether forward reaction exo or endo

Answer 26

• exothermic as % decrease as temp increase
• system opposes change by taking in heat, bringing equilibrium left (endothermic)

Question 27

Graphs shows % product decrease as temp increase. Explain whether reaction involves increase or decrease in moles

Answer 27

• decrease in moles since % product increases
• system oppose increase by shifting equilibrium right