Equilibria

Question 1

Name 3 conditions for equilibrium

Answer 1

1) can only be reached in a closed system
2) no more reactants are added or removed
3) properties of the system do not change with time eg conc or pressure

Question 2

Le chatelier’s principle

Answer 2

Position of equal will shift to oppose the change

Question 3

3 factors that affect the position of equilibrium and how they change said position of the equilibrium

Answer 3

1)CONCENTRATION
If u add a chemical (increase concentration) the equilibrium will shift to remove it. If you remove a chemical (decrease concentration) the equilibrium will shift to move more of it
2) PRESSURE
Increases pressure = equilibrium shifts to the side with fewer moles of gas
Decrease pressure = equilibrium shifts to the side with more moles of gas
3) TEMPERATURE
Increase temp = equilibrium moves to endothermic direction to decrease temp
Decrease temp = equilibrium shifts to exothermic direction to increase tempt

Question 4

True or False ? “Pressure only affects the position of chemical equilibria that involve liquids” Explain your answer.

Answer 4

FALSE

Pressure only affects the position of chemical equilibria that involve gases

Question 5

How does adding a catalyst affect an equilibrium mixture ? Explain your answer

Answer 5

I’d doesn’t affect the equilibrium

The catalyst increases the rate of both the forward and backward reaction EQUALLY

Question 6

What way does the position of equilibrium shift when you increase the concentration of reactants/ decrease the concentration of products

Answer 6

Equilibrium will shift to the right
To decrease the concentration of reactants /increase the concentration of products

Question 7

What way does the position of equilibrium shift when you decrease the concentration of reactants/ increase the concentration of products

Answer 7

Equilibrium will shift to the left

To increase the concentration of reactants / decrease the concentration of products

Question 8

Fill the blank “if equilibrium shifts to the ______ , yield increases”

Answer 8

RIGHT

Question 9

Fill the blank “if equilibrium shifts to the ______ , yield decreases”

Answer 9

LEFT

Question 10

What is the harber process ? What is the product used for ?

Answer 10

The synthesis of ammonia from nitrogen and hydrogen

Used in production of fertiliser, synthetic fabrics and plastics.

Question 11

Explain the optimum temperature used for the Haber process - remember sometimes compromises are needed

Answer 11

• it is an exothermic reaction so the forward reaction is exothermic
  -the best yield would be at a low temperature as the equilibrium will shift to the right (exo) to opposite the this change

HOWEVERRRRR

• low temp means a very slow rate of reaction so a compromise temp is used 650-720K

Question 12

Explain the optimum pressure used for the Haber process - remember sometimes compromises are needed

Answer 12

• high pressure would move the equilibrium to the right (side with fewer number of gas moles
• yield would increase

HOWEVERRRRRR

• high pressure is expensive to generate and need complex equipment

Question 13

Homogeneous equilibrium

Answer 13

A system where the reactants and products are in the same phase

Question 14

What is Kc? What is the general equation for finding Kc ?

Answer 14

Kc = the ratio of concentration of products to the reactants

Kc= [products] / [reactants]

Question 15

Fill the blanks. “Exothermic reaction have a 1) ________ enthalpy change and endothermic reactions have a 2) ________ enthalpy change”

Answer 15

1) negative
2) positive

Question 16

What factors affect the value of equilibrium constant Kc?

Answer 16

Temperature ONLY.

Question 17

The affects of temperature on yield is proportional to the affect of temperature on Kc. TRUE OR FALSE

Answer 17

TRUE.