Equilibria

Question 1

Give an example of a reversible reaction?

Answer 1

Carboxylic acid+ alcohol<> ester +water

Question 2

What happens to the concentration of products and reactants as the reaction proceeds?

Answer 2

Product concentration increases and the reactant concentration decreases

Question 3

When is equilibrium reached?

Answer 3

When the concentration of the reactants and products remains constant

Question 4

What is a closed system?

Answer 4

One which is sealed

Question 5

When is a reversible reaction said to be at dynamic equilibrium?

Answer 5

Rate of forward reaction= rate of reverse reaction

Question 6

What are the 3 rules for dynamic equilibrium?

Answer 6

Concentrations of reactants and products remain constant
Concentrations are not usually equal
The reaction has not stopped

Question 7

How can a reversible reaction’s equilibrium be altered ?

Answer 7

Altering the conditions of the reaction

Question 8

What are the 3 things which can alter the equilibrium?

Answer 8

Concentration
Temperature
Total pressure

Question 9

If a chemical system at equilibrium experiences a change in concentration, temperature or total pressure then what will the equilibrium do?

Answer 9

Shift to counter-act the imposed change

Question 10

What are the 2 rules for equilibrium?

Answer 10

If equilibrium moves to the right ; more products are produced

If equilibrium moves to the left; more reactants will be produced

Question 11

Where the equilibrium move to if there is an increase in concentration of any reactant?

Answer 11

Right

Question 12

Where the equilibrium move to if there is an increase in concentration of any product?

Answer 12

Left

Question 13

Where the equilibrium move to if there is an decrease in concentration of reactants?

Answer 13

Left

Question 14

Where the equilibrium move to if there is an decrease in concentration of products?

Answer 14

Right

Question 15

What happens if an alkali I.e OH- ions are added?

Br2+H2O<>2H+ + Br- + BrCl-

Br2 red
H+ colourless

Answer 15

The OH- ions of the alkali neutralise and remove the H+ ions of the acid. The equilibrium will shift to the right to replace the H+ ions. As a result the solution will appear colourless.

Question 16

What happens if an acid I.e H+ ions are added?

Br2+H2O<>2H+ + Br- + BrCl-

Br2 red
H+ colourless

Answer 16

Adding an acid increases the H+ ion concentration. As a result the equilibrium shifts to the left to remove H+ ions and the solution will appear red

Question 17

What is the enthalpy change for an exothermic reaction?

Answer 17

negative

Question 18

What is the enthalpy change for an endothermic reaction?

Answer 18

positive

Question 19

What effect does an increase in temperature have?

Answer 19

energy increases> positive value> ENDOTHERMIC

Question 20

What does an increase in temperature do to the equilibrium?

Answer 20

equilibrium moves in ENDO- direction

Question 21

What effect does a decrease in temperature have?

Answer 21

energy decreases>negative value> EXOTHERMIC

Question 22

What does a decrease in temperature do to the equilibrium?

Answer 22

Equilibrium moves in EXO- direction

Question 23

What is changes in pressure only important for?

Answer 23

reactions involving gases

Question 24

What must you only look at when answering questions on the effect of changing pressure?

Answer 24

state symbols involving gases

Question 25

What effect does increasing pressure have?

Answer 25

volume decreases, equilibrium moves to the side with the lowest volume, hence producing more of the molecules.

Question 26

What effect does decreasing pressure have?

Answer 26

volume increases, equilibrium moves to side with largest volume, hence producing more of the molecules.

Question 27

What effect would a change in pressure have if there is no overall decrease or increase in number of gaseous molecules i.e. same number of gaseous molecules on each side?

Answer 27

no effect

Question 28

What do gases occupy much more than solids or liquids?

Answer 28

much more space

Question 29

What will a catalyst increase the rate of ?

Answer 29

the rate of the forward and reverse reaction

Question 30

As a catalyst increases the rate of the forward and reverse reaction, what happens to the dynamic equilibrium?

Answer 30

it will be achieved quicker

Question 31

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

Answer 31

NO EFFECT.

Question 32

What are the laws of equilibrium used by and why?

Answer 32

industrial chemists to increase the yield of products

Question 33

What is ammonia?

Answer 33

an important feedstock and can be used to make fertilisers, dyes, explosives and household cleaners

Question 34

What is industry organised to make ?

Answer 34

as much profit as possible

Question 35

What is the result of industries which are organised to make as much profit as possible?

Answer 35

reaction conditions are sometimes altered for economical reasons

Question 36

What might it be inefficient to have a low temperature even if this favours more product to be produced?

Answer 36

The reaction may be too slow and not economical. Therefore a moderate temp is used.

Question 37

What might it be inefficient to have high pressure even if this favours more product to be produced?

Answer 37

the equipment required for dealing with high pressure will be too expensive. Therefore, a moderate pressure will be used.

Question 38

What happens to unreacted reactants and what will this favour?

Answer 38

recycled. produce more product.

Question 39

What happens to the product(s)and what will this favour?

Answer 39

continuously removed. produce more product

Question 40

What do many industrial processes use?

Answer 40

a catalyst

Question 41

What does a catalyst not alter and what does it do?

Answer 41

the position of the equilibrium but does lower the quantity of energy required for the reaction.

Question 42

What does using a catalyst also do?

Answer 42

speed up the reaction and makes the overall process more economical