Dynamic Equilibrium

Question 1

What type of reaction can reach dynamic equilibrium?

Answer 1

Reversible reactions.

Question 2

What happens to the speed of the forward reaction when most of the reactants are used up?

Answer 2

The forward reaction slows down.

Question 3

What happens to the speed of the back reaction when most of the reactants are used up and why?

Answer 3

More products are being formed so the reaction speeds up.

Question 4

What is dynamic equilibrium?

Answer 4

This is where the forward and back reaction go at the same rate.

Question 5

How can you tell when dynamic equilibrium has been reached?

Answer 5

The amount of reactants and products doesn’t change.

Question 6

What happens to the concentration of reactants and products at equilibrium?

Answer 6

They stay constant.

Question 7

What is required in order for a dynamic equilibrium to be achieved?

Answer 7

The reactions have to happen in a closed system.

Question 8

What is meant by a closed system?

Answer 8

This is where nothing can get in or out.

Question 9

What is Le Chatelier’s principle?

Answer 9

When a system in equilibrium is subjected to an external change the system readjusts itself to minimise the effect of that change.

Question 10

What happens if you increase the concentration of the reactant?

Answer 10

The position of equilibrium is shifted to the right.

Question 11

Why is the position of equilibrium shifted to the right when the concentration of the reactant is increased?

Answer 11

The equilibrium makes or product to remove some of the reactant.

Question 12

What happens if the concentration of the products is increased?

Answer 12

The position of the equilibrium shifts to the left as the back reaction goes faster.

Question 13

What is the effect of decreasing the concentration?

Answer 13

This has the opposite effect.

Question 14

What happens if you increase the pressure of a gas?

Answer 14

The equilibrium shifts to the side with the fewest gas molecules which reduces the pressure.

Question 15

What happens to the equilibrium is you decrease the pressure?

Answer 15

The equilibrium shifts to the side with the most gas molecules. This raises the pressure again.

Question 16

What happens to the position of equilibrium if you increase the pressure?

Answer 16

The equilibrium shifts to the endothermic direction.

Question 17

How can you tell which is the endothermic direction?

Answer 17

This is the direction that has a positive AH value.

Question 18

Why does the equilibrium shift to the endothermic direction when the temperature is increased?

Answer 18

To absorb the heat.

Question 19

What happens to the heat when the temperature is decreased?

Answer 19

Heat is removed.

Question 20

In which direction does the equilibrium shift when the temperature is increased?

Answer 20

It shifts to the exothermic direction to try and replace the heat.

Question 21

Do catalysts have an effect on the position of equilibrium?

Answer 21

No

Question 22

Do catalysts have an effect on equilibrium?

Answer 22

If a catalyst is used, equilibrium will be reached faster.

Question 23

What type of reaction produces ethanol?

Answer 23

A reversible reaction.

Question 24

What are the reactants of ethanol formation?

Answer 24

Ethene and steam

Question 25

What are the conditions for the reaction of ethanol?

Answer 25

60-70atmospheres, 330C with a phosphoric(V) acid catalyst.

Question 26

What type of temperature is favoured by the reaction to make ethanol?

Answer 26

Lower temperatures as this creates a bigger yield.

Question 27

What is a problem with lower temperatures?

Answer 27

The reaction rate is slower.

Question 28

Why is a high pressure used to make ethanol?

Answer 28

It increases the rate of reaction.

Question 29

What is the problem with high pressures?

Answer 29

They are expensive and dangerous. Side reaction can also occur.