Equilibria

Question 1

What is meant by the term ‘dynamic equilibrium’?

Answer 1

A reaction in a closed system, in which the concentrations remain the same.

Question 2

State Le Chatelier’s principle.

Answer 2

If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance.

Question 3

What would happen if the concentration of a reactant was increased in a reaction?

Answer 3

More products would be formed, position of equilibrium shifts to the right.

Question 4

Given that there are more moles of gas on the right hand side of the reaction, state the outcome of an increase in pressure.

Answer 4

Less products would be formed, position of equilibrium shifts to the left.

Question 5

Given that a reaction in equilibria is exothermic, state the outcome of an increase in temperature.

Answer 5

Less products would be formed, position of equilibrium shifts to the left.

Question 6

What can be used in equilibria to speed up the reaction, without changing the position of equilibrium.

Answer 6

Catalyst.

Question 7

How does a catalyst work?

Answer 7

They provide an alternative route to the reaction which has a lower activation energy.

Question 8

What is the symbol equation for the reaction that forms ammonia in equilibrium?

Answer 8

N2(g) + 3H2 2NH3(g)

Question 9

How do we acquire the reactants needed for the ammonia reaction?

Answer 9

Nitrogen comes from the air.

Hydrogen comes from water and natural gas.

Question 10

What is ammonia used for?

Answer 10

Mostly used for fertilisers.

Also used for making nylon, explosives, drugs and dyes.

Question 11

In equilibrium reactions, what do we visually see?

Answer 11

Nothing - the macroscopic properties remain the same, changes only occur at the microscopic level.

Question 12

What catalyst is used for the reaction to produce ammonia and what size is it?

Answer 12

Iron. Pea-sized.

Question 13

How often must the catalyst be replaced in the production of ammonia and why?

Answer 13

Every 5 years due to impurities.

Question 14

What conditions are used in the production of ammonia?

Answer 14

20,000kPa.

670K.

Question 15

What is the symbol equation for the formation of ethanol in equilibrium?

Answer 15

C2H4(g) + H2O(g) C2H5O (g)

Question 16

What conditions are used in the production of ethanol?

Answer 16

6500kPa.

570K.

Question 17

Why can the pressure not be too high in the production of ethanol? Not including safety, environmental or economical reasons.

Answer 17

This might cause the formation of polythene.

Question 18

What catalyst is used in the formation of ethanol?

Answer 18

Phosphoric acid/ H3PO4 (absorbed on silica).

Question 19

Why would an increase in the concentration of steam in this reaction cause a problem?

Answer 19

It would dilute the acid catalyst.

Question 20

What is the symbol equation for the formation of methanol in equilibrium?

Answer 20

CO(g) + 2H2(g) CH3OH(g)

Question 21

What conditions are used in the production of methanol?

Answer 21

10,000kPa.

500K.

Question 22

What is the principal use of methanol?

Answer 22

Chemical feedstock - a starting material for making other chemicals.

Question 23

In the production of ammonia, ethanol and methanol, a very low yield of product is achieved. How can a higher yield be achieved without changing the reaction conditions?

Answer 23

Recycle the unreacted reactants/ feed them back into the reactor.

Question 24

In the production of ammonia, ethanol and methanol, why is a high temperature used despite the reaction being exothermic?

Answer 24

To speed up the process/ faster rate of reaction.

Question 25

In the production of ammonia, ethanol and methanol, why is a higher pressure not used than the figures that are used?

Answer 25

More safety equipment needed.
More energy needed to be pumped.
Therefore high energy costs.