Equilibrium 1

Question 1

What do all reversible reactions eventually reach?

Answer 1

A dynamic equilibrium state

Question 2

When does dynamic equilibrium occur?

Answer 2

When the rates of the forward and backward reactions are equal

Question 3

What is the concentrations of the products and reactants at dynamic equilibrium?

Answer 3

They are constant and the reaction is continuous

Question 4

What expression do we use to describe the composition of the equilibrium mixture?

Answer 4

Position of equilibrium

Question 5

If the position of equilibrium favours one side more than the other, what does this mean?

Answer 5

There is more of that side
e.g. if the position is towards the left, the mixture will contain mostly reactants

Question 6

What does Le Chateliers principle state?

Answer 6

If an external condition is changed the equilibrium will shift to oppose the change (and try to reverse it)

Question 7

What happens if the temperature is increased or decreased in an equilibrium mixture?

Answer 7

If increased, will shift to oppose and move in the endothermic direction to try to reduce temperature by absorbing heat
If decreased, will shift to oppose and move in exothermic reaction to try to increase temperature by releasing heat

Question 8

Why do we need a compromise temperature in equilibrium mixtures?

Answer 8

Low temperatures may give a high yield of product but will also result in slow rates of reaction

Question 9

What happens if pressure is increased or decreased in an equilibrium mixture?

Answer 9

Increasing will cause equilibrium to shift towards side with fewer moles of gas to reduce pressure
Decreasing causes it to shift to side with more moles of gas to decrease pressure

Question 10

What happens if the pressure changes in an equilibrium mixture but both sides have the same number of moles of gas?

Answer 10

It will have no effect on the position of equilibrium

Question 11

Why can’t we always increase the pressure in an equilibrium mixture?

Answer 11

While it may give a higher yield of product and faster rate, it is expensive to produce - high electrical energy costs to pump gas - and equipment is expensive - to contain high pressure

Question 12

What happens if the concentration of the reactants increases in an equilibrium mixture?

Answer 12

The position of equilibrium will shift towards the right - to the products
(and vice versa if the concentration of the products is increased)

Question 13

What is the effect of a catalyst on equilibrium?

Answer 13

There is no effect on the position but it will speed up the rate at which the equilibrium is achieved

Question 14

What will catalysts do for industrial processes?

Answer 14

Lower energy costs

Question 15

How can we improve the overall yields of industrial processes?

Answer 15

By recycling unreacted reactants back into the reactor

Question 16

What is Kc?

Answer 16

Equilibrium constant

Question 17

What is the equation for a generalised reaction?

Answer 17

mA + nB = Cp + Dq

Question 18

What is the equation for the equilibrium constant?

Answer 18

[C]^p [D]^q / [A]^m [B]^n

Question 19

What is not included in heterogenous Kc expressions and why?

Answer 19

Liquid and solid concentrations as they are constant

Question 20

What does a larger Kc mean?

Answer 20

The greater the amount of products

Question 21

What do we say if Kc is small?

Answer 21

The equilibrium favours the reactants

Question 22

What is the only variable that changes Kc?

Answer 22

Temperature

Question 23

What does it mean if Kc is approximately 1?

Answer 23

Equal product and reactant

Question 24

What does it mean if we have a homogenous reaction?

Answer 24

All reactants and products are in the same state(phase)

Question 25

In industrial processes, what can be done to increase the atom economy of a reversible reaction?

Answer 25

Remove the product Recycle unreacted reactants