Study Guide

Question 1

Reaction Rate

Answer 1

The rate of a reaction is a measure of how quickly a reactant is used up or a product is formed.

Question 2

The collision Theory

Answer 2

For a chemical reaction to occur the reactants must be in the correct orientation and have enough kinetic energy.

Question 3

Activation Energy

Answer 3

The minimum amount of energy that colliding particles must have for them to react.

Question 4

Fast Reactions vs. Snow Reactions

Answer 4

fast reactions finish sooner (when the line becomes horizontal) than slow reaction.

Question 5

If the concentration of a reacting solution or the pressure of a reacting gas is increased:

Answer 5

the reactant particles become more crowded
the frequency of collisions between reactant particles increases
the rate of reaction increases

Question 6

If the surface area to volume ratio of a reacting solid is increased:

Answer 6

more reactant particles are exposed at the surface
the frequency of successful collisions between reactant particles increases
the rate of reaction increases

Question 7

Which reaction takes the longest time, where there is powder or where there are lumps

Answer 7

Powder, the reason why is because there is more surface area compared to the lumps. When there is a greater surface area the reactant particles exposed have increased. When there is more reactant particles exposed then the chances of collisions happening increases.

Question 8

If the temperature of the reaction mixture is increased:

Answer 8

reactantparticles move more quickly
the energy of the particles increases
the frequency of successful collisions between reactant particles increases
the proportion of collisions which are successful also increases
the rate of reaction increases

Question 9

Successful Collision

Answer 9

A collision between reactant particles with enough energy, eg the activation energy or more, to produce a reaction.

Question 10

A catalyst is a substance that:

Answer 10

increases the rate of a reaction, but
does not alter the products of the reaction, and
is unchanged chemically and in mass at the end of the reaction

Question 11

How do catalysts work?

Answer 11

A catalyst allows an alternative reaction pathway that has a lower activation energy than the uncatalysed reaction. This does not change the frequency of collisions.

Question 12

Enzyme

Answer 12

A biological catalyst

Question 13

Endothermic Reaction

Answer 13

An endothermic reaction is a chemical reaction that takes in energy from the surroundings. The energy is usually transferred as heat energy: the reaction absorbs heat. This makes the environment around it colder.

Question 14

Exothermic Reaction

Answer 14

An exothermic reaction is a chemical reaction where the substances reacting release energy as heat. An example of this is combustion. Exothermic reactions transfer energy to the surroundings.

Question 15

Optimum Temperature

Answer 15

The temperature where the reaction rate will be the fastest

Question 16

When the temperature exceeds the optimum temperature why does the reaction rate decrease?

Answer 16

When at high temperatures the shape of the enzyme changes and can no longer interlock with a substrate, this means that it is denatured

Question 17

Products

Answer 17

The outcome of the chemical reaction

Question 18

Reactants

Answer 18

The materials used/taking part in the chemical reaction

Question 19

On a graph showing mass of reactant used against time, what does the gradient of the line show?

Answer 19

The gradient shows the rate of reaction at the time it is calculated. The mean rate is calculated from the total mass used up divided by the time taken for the reaction to finish.

Question 20

What happens to the activation energy for a reaction in the presence of a catalyst?

Answer 20

A catalyst allows an alternative reaction pathway that has a lower activation energy than the uncatalysed reaction.