3d) - Equilibria

Question 1

In a closed system, when do reversible reactions attain a state of dynamic equilibrium

Answer 1

In a closed system, reversible reactions attain a state of dynamic equilibrium when the rates of of forward and reverse reactions are equal.

Question 2

What is rarely equal at equilibrium

Answer 2

At equilibrium the concentration of reactants and products remain constant but are rarely equal

Question 3

How do chemists maximise profit

Answer 3

To maximise profits, chemists employ strategies to move the position of equilibrium in favour of the product

Question 4

What is the explanation of concentration (A+D)

Answer 4

A + B reversible C + D

• addition of A (one reactant) or subtraction of D (one product) favours the forward reaction and shifts the equilibrium to the right
• as the equilibrium has to remove additional (A) so forward reaction uses up more A

Question 5

What is the explanation of concentration (C+A)

Answer 5

A + B reversible C + D

• addition of C (one product) or subtraction of A (one reactant) favours the reverse reaction and shifts the equilibrium to the left
• this is because the equilibrium is trying to regain its balance by pushing backward reaction to the left therefore producing more reactants
• Taking away A would have same affect as C + D would have to react to produce more A

Question 6

Summary of effect of concentration on equilibrium

Answer 6

Concentration. Effect on equilibrium position

Addition of reactant or removal product Equilibrium shifts to the right

Addition of product or removal of reactant Equilibrium shifts to the left

Question 7

What happens if the forward reaction is favoured

Answer 7

If the forward reaction is favoured we say the equilibrium has moved to the right

Question 8

What happens if the reverse reaction is favoured

Answer 8

If the reverse reaction is favoured we say the equilibrium has moved to the left

Question 9

Effect of changing temperature on an endothermic reaction

Answer 9

A + B reversible C + D

• increasing the temperature of A + B will shift equilibrium to the right the forward reaction takes in energy so it moves to the right
• decreasing the temperature of C + D will shift equilibrium to the left the reverse reaction gives out energy so equilibrium shifts to the left

Question 10

Which reactions will equilibrium favour when temperature is changed

Answer 10

If the temperature is increased the equilibrium will favour the froward endothermic reaction. The equilibrium moves to the right

If the temperature is decreased the equilibrium will favour the reverse exothermic reaction. The equilibrium moves to the left

Question 11

Temperature summary

Answer 11

Temperature Effect on equilibrium position

Increase Shifts in direction of the endothermic reaction

Decrease Shifts in direction of exothermic reaction

Question 12

What is the effect of catalyst on equilibrium

Answer 12

The use of a catalyst does not change the equilibrium position it only enables the position of equilibrium to be reached more quickly

Question 13

What is the effect of increasing pressure on equilibrium

Answer 13

• increasing the pressure will cause the equilibrium to move to the side with fewer particles to reduce the number of particles
• decreasing the pressure will cause the equilibrium to move to the side with more particles to increase the number of particles

Question 14

What do hydrogen and hydroxide ions do to eachother

Answer 14

Hydrogen and hydroxide ions remove each other

Question 15

When asked the addition of which of the following substances will affect equilibrium

Answer 15

Write out ionic formula of all options