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Higher Chemistry Unit 3 Chemistry in Society > Equilibria > Flashcards

Flashcards in Equilibria Deck (42)
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1
Q

Give an example of a reversible reaction?

A

Carboxylic acid+ alcohol<> ester +water

2
Q

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

A

Product concentration increases and the reactant concentration decreases

3
Q

When is equilibrium reached?

A

When the concentration of the reactants and products remains constant

4
Q

What is a closed system?

A

One which is sealed

5
Q

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

A

Rate of forward reaction= rate of reverse reaction

6
Q

What are the 3 rules for dynamic equilibrium?

A

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

7
Q

How can a reversible reaction’s equilibrium be altered ?

A

Altering the conditions of the reaction

8
Q

What are the 3 things which can alter the equilibrium?

A

Concentration
Temperature
Total pressure

9
Q

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

A

Shift to counter-act the imposed change

10
Q

What are the 2 rules for equilibrium?

A

If equilibrium moves to the right ; more products are produced

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

11
Q

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

A

Right

12
Q

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

A

Left

13
Q

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

A

Left

14
Q

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

A

Right

15
Q

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

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

Br2 red
H+ colourless

A

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.

16
Q

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

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

Br2 red
H+ colourless

A

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

17
Q

What is the enthalpy change for an exothermic reaction?

A

negative

18
Q

What is the enthalpy change for an endothermic reaction?

A

positive

19
Q

What effect does an increase in temperature have?

A

energy increases> positive value> ENDOTHERMIC

20
Q

What does an increase in temperature do to the equilibrium?

A

equilibrium moves in ENDO- direction

21
Q

What effect does a decrease in temperature have?

A

energy decreases>negative value> EXOTHERMIC

22
Q

What does a decrease in temperature do to the equilibrium?

A

Equilibrium moves in EXO- direction

23
Q

What is changes in pressure only important for?

A

reactions involving gases

24
Q

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

A

state symbols involving gases

25
Q

What effect does increasing pressure have?

A

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

26
Q

What effect does decreasing pressure have?

A

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

27
Q

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?

A

no effect

28
Q

What do gases occupy much more than solids or liquids?

A

much more space

29
Q

What will a catalyst increase the rate of ?

A

the rate of the forward and reverse reaction

30
Q

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

A

it will be achieved quicker

31
Q

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

A

NO EFFECT.

32
Q

What are the laws of equilibrium used by and why?

A

industrial chemists to increase the yield of products

33
Q

What is ammonia?

A

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

34
Q

What is industry organised to make ?

A

as much profit as possible

35
Q

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

A

reaction conditions are sometimes altered for economical reasons

36
Q

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

A

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

37
Q

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

A

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

38
Q

What happens to unreacted reactants and what will this favour?

A

recycled. produce more product.

39
Q

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

A

continuously removed. produce more product

40
Q

What do many industrial processes use?

A

a catalyst

41
Q

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

A

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

42
Q

What does using a catalyst also do?

A

speed up the reaction and makes the overall process more economical