C6 Reversible Reactions (pg 147)

Question 1

Reversible reactions will reach Equillibrium, what do this mean?

Answer 1

It means a state of physical balance.

(a state of which opposing forces or actions are balanced, so that one is not stronger or greater than the other)

Question 2

In the diagram on page 147, the equation shows a reversible reaction, what do this mean?

Answer 2

The products (C and D) can react to form the reactants (A and B) again.

Question 3

As the reactants react in diagram on page 147, their concentrations fall, what do this mean?

Answer 3

the forward reaction will slow down (see page 143). But as more and more products are made and their concentrations rise, the backward reaction will speed up.

After a while the forward reaction will be going at exactly the same rate as the backward one, - the system is at equilibrium

Question 4

At equibilbrium, both reactions are still happening, but there is no overall effect (it’s a dynamic equilibrium), what do this mean?

Answer 4

This means the concentractions of reactants and products have reached a balance and wont change.

Question 5

When is Equilibrium reached?

Answer 5

it is only reached if the reversible reaction takes place in a ‘closed system’.

Question 6

What do a ‘closed system’ mean?

Answer 6

It means that none of the reactants or products can escape and nothing else can get in.

Question 7

Will Reversible reactions reach equilibrum?

Answer 7

Yes

Question 8

When a reaction’s at equilibrium does it mean the amounts of reactants and products are equal?

Answer 8

no.

Question 9

If the equilibrium lies to the right, the concentration of products is less or greater than that of the reactants?

Answer 9

It is greater

Question 10

If the equilibrium lies to the left, the concentration of reactants is less or greater than that of the products?

Answer 10

it is greater

Question 11

The position of equilibrium depens on what conditions (as well as the reaction itself)?

Answer 11

The temperature

The pressure (this only effects equilibria involving gasses)

The concentration of the reactants and the products

eg:

ammonium chloride &raquo_space;»»»»
««««&laquo_space; ammonia + hydrogen chloride

Heating this reaction moves the equilibrium to the right (more ammonia and hydrogen chloride), and cooling it moves it to the left (more ammonium chloride)

Question 12

What is the position of equilibrium?

Answer 12

can be on the right or the left

Question 13

Reversible Reactions can be?……

Answer 13

Endothermic and Exothermic

Question 14

In reversible reactions, if the reaction is endothermis in one direction, what will it be in the other direction?

Answer 14

Exothermic.

Question 15

The energy transferred from the surroundings by the endothermic reaction is equal to what?

Answer 15

its equal to the energy transferred to the surroundings during the exothermis reaction

(see page 138 for more on endothermic and exothermis reactions).

Question 16

What is a good example of thermal decomposition of hydrated copper sulfate?

Answer 16

(endothermic)
hydrated copper sulfate&raquo_space;»»»»
««««&laquo_space; anhydrous copper
sulfate + water

                                   (exothermic)

Anhydrous just means without water
hydrated means with water

Question 17

If you heat blue hydrated copper (II) sulfate chrystals, it drives the water off and leaves white anhydrous copper (II) powder. Is this ‘endothermic’ or ‘exothermic’?

Answer 17

This is Endothermic

so if you add a couple of drops of water to the white powder you get the blue chrystals back again. This is exothermic

Question 18

What is Endothermic mean?

Answer 18

of a reaction or process accompanied by or requiring the absorption of heat.

Question 19

What is Exothermic?

Answer 19

of a reaction or process accompanied by the release of heat

Question 20

What does it mean if a system is at equilibrium? (1 mark)

Answer 20

A system is at equilibrium when both the forward and reverse reactions are happening at the same rate (1 mark)

(make sure you understand everything in this section before you move on to the next one, as it will help with further chapters).