Chemical Equilibria

Question 1

What happens if you increase the pressure under a dynamic equilibrium?

Answer 1

• the position of equilibrium will shift to the side where there are fewer moles of gas to oppose the change.
• This causes a decrease in pressure

Question 2

What happens if you decrease the pressure under a dynamic equilibrium?

Answer 2

• the position of equilibrium will shift to the side where there are more moles of gas to oppose the change
• This causes a increase in pressure.

Question 3

Would increasing the pressure give a higher yield of product?

Answer 3

Yeah, and will produce a faster rate.

Question 4

2SO2 + O2 —> 2SO3

What happens if you increase the concentration the reactant?

Answer 4

The equilibrium tries to get rid of extra reactant, so it makes more product so the equilibrium shifts to the right

Question 5

2SO2 + O2 —> 2SO3

What happens if you increase the concentration of the product?

Answer 5

Equilibrium tries to move extra product, so equilibrium shifts to the left
• the reverse reaction goes faster

Question 6

2SO2 + O2 —> 2SO3

In an exothermic reaction, what happens if you increase the temperature?

Answer 6

Position of equilibrium shifts to the left so there’s more reactants in the system.

Question 7

2SO2 + O2 —> 2SO3

In an exothermic reaction, what happens if you decrease the temperature?

Answer 7

Position of equilibrium shifts to the right, so there’s more products in the system

Question 8

In an endothermic reaction, 2HI —> H2 + I2

What happens if you increase the temperature?

Answer 8

The position of equilibrium shifts to the right so there’s more product in the system.

Question 9

In an endothermic reaction, what happens when you decrease the temperature?

Answer 9

Position of equilibrium shifts to the left, there’s more reactants in the system.

Question 10

What is heterogenous equilibrium?

Answer 10

Where the reactants and products are in different states

Question 11

What is homogenous equilibrium?

Answer 11

Where the reactants and products are in the same state.

Question 12

What affect does a catalyst have on the position of equilibrium?

Answer 12

None, but it affects the rate at which equilibrium is established
Use of catalysts allow manufactures to run reactions at low temperatures

Question 13

What is Le Chateliers principle?

Answer 13

When a system under dynamic equilibrium subjected to a change, the equilibrium will shift to oppose the change

Question 14

What are features of a chemical equilibria?

Answer 14

• when the rate of the forward reaction = the rate of the reverse reaction
• reaction remains in dynamic equilibrium if the system is isolated ( one where there is no exchange of matter/energy between the system and its surroundings )
• reactants are being used to form products and and the products breaking down to form reactants ( temp/pressure stay constant )

Question 15

What happens if the number of moles of gas is the same on both sides?

Answer 15

• the changing pressure will have no effect on the position of equilibrium

Question 16

Effect of temperature?

Answer 16

• if the temperature is increased, the equilibrium will shift to oppose this and move in the endothermic direction to try and reduce the temperature by absorbing heat
( endothermic = fall in temperature )

• temperature is decreased the equilibrium will shift to oppose this and move in the exothermic direction to try and increase the temperature by giving out heat
( exothermic = rise in temperature )

Question 17

Effects of temperatures?

Answer 17

• low temperatures may give a higher yield of product but will also result in a slow rate of reaction
• a compromise temperature is used that gives a reasonable yield and rate

Question 18

Effects of pressure?

Answer 18

• a high pressure will increase the rate of rection and also increase the yield but it increases the cost and equipment is expensive to contain high pressure

Question 19

Conditions used in ammonia plants are?

Answer 19

• temperature : 400-500 degrees
• pressure : 200 atm
• catalyst : iron

Question 20

How to improve the yields of processes?

Answer 20

• recycling unreacted reactants back into the reactor