The Rate and Extent of Chemical Change

Question 1

What is the calculation for mean rate of reaction?

Answer 1

amount of reactant used or product formed/time

Question 2

What is amount of reactant measured in?

Answer 2

Moles (mol).

Question 3

Explain collision theory relating to temperature.

Answer 3

In a hot reaction mixture the particles move more quickly- they collide more often and with greater energy, so more collisions are successful.

Question 4

Explain collision theory in relation to concentration.

Answer 4

At higher concentrations, the particles are crowded closer together- they collide more often, so there are more successful collisions. (Increasing the pressure in a gas has the same effect).

Question 5

Explain collision theory in relation to surface area.

Answer 5

Small pieces of a solid reactant have a large surface area in relation to their volume. More particles are exposed and available or collisions, so there are more collisions and a faster reaction.

Question 6

What is a catalyst?

Answer 6

A substance that increases the rate of a chemical reaction without being used up in the process.

Question 7

What is a reversible reaction?

Answer 7

A reaction that can go forwards and backwards (the products can react to produce the original reactants).

Question 8

What is a closed system?

Answer 8

In a closed system no reactants are added and no products are removed.

Question 9

When is equilibrium achieved?

Answer 9

When the rate of the forward and backward reaction in a closed system are equal, an equilibrium is achieved.

Question 10

What is Le Chatelier’s Principle?

Answer 10

It states that if a system in equilibrium is subjected to a change in conditions, then the system shifts to resist the change.