C8: Rates of Reaction

Question 1

Avg. Rate of Reaction=

Answer 1

Amount of reactant used or amount of product formed / Time

Question 2

4 factors that affect the Rate of Reaction

Answer 2

Temp.
SA
Conc. of solutions/ Pressure of gases
Presence of a catalyst

Question 3

Collision Theory

Answer 3

An explanation of chemical reactions in terms of reacting particles colliding with sufficient energy for a reaction to take place.

Question 4

Activation Energy

Answer 4

The minimum energy needed for a reaction to take place.

Question 5

What 2 factors make a reaction more likely to occur?

Answer 5

> Increasing the frequency of particle’s collisions.

> Increasing the energy they contain when they collide.

Question 6

What effect does a larger Surface Area have on the rate of reaction?

Answer 6

It does not result in collisions with more energy, but it does increase the frequency of collisions.

Question 7

Increasing the surface area of an object…

Answer 7

…increases its rate of reaction.

Question 8

How does raising the temperature affect the rate of reaction?

Answer 8

RoR increases.

Question 9

Why does heating a substance increase its rate of reaction?

Answer 9

> When a substance is heated, energy is transferred to its particles.
This means that the particles move around faster, causing them, to collide more frequently.
This gives them more chances to react.
(THIS FACTOR IS LESS IMPORTANT THAN THE FACT THAT THE COLLISIONS CONTAIN MORE ENERGY)

Question 10

How does heating a substance affect a particle’s energy?

Answer 10

> Because the particles are moving faster, they have more energy.
This results in a higher proportion of particles having greater energy than activation energy.
This effects the rate of reaction.

Question 11

What is the consequence of increasing the concentration of reactants in a solution?

Answer 11

It increases the rate of reaction because there are more particles of the reactants, making the collisions more frequent.

Question 12

What is not affected by an increase in the pressure or concentration of a substance?

Answer 12

The energy with which particles collide. It only affects the frequency of collisions.

Question 13

What is the consequence of increasing the pressure of reacting gases?

Answer 13

Gas particles are squashed closer together, which increases the chance of collisions and reactions.

Question 14

Catalyst

Answer 14

A substance that increases the rate of reaction.

Question 15

When is Iron used as a catalyst?

Answer 15

Ammonia production

Question 16

When is Platinum used as a catalyst?

Answer 16

Nitric acid production

Question 17

What can we do to make catalysts as effective as possible?

Answer 17

Increase their SA

Question 18

When Platinum and Palladium used as catalysts?

Answer 18

In Catalytic Converters inside car engines.

Question 19

Positives of using catalysts.

Answer 19

> They don’t get used up- only a small amount is needed.
They’re good for the environment (don’t burn as many fossil fuels).
Often cheaper than paying for extra energy.

Question 20

Negatives of using catalysts.

Answer 20

> Often expensive.