CC14

Question 1

What is the rate of reaction?

Answer 1

The rate of reaction is the speed at which reactants are turned into products.

Question 2

How can rate of reaction be controlled?

Answer 2

Rates of reaction can be controlled by altering variables (e.g. altering the concentration of the solution and the size of pieces of solid reactant will change the rate of reaction)

Question 3

What does the gradient tell us in a graph when we are trying to find the rate of reaction (concentration-time graph)?

Answer 3

The gradient of the graph indicates the rate of reaction : the steeper the graph, the faster the reaction.

Question 4

Why are reaction rates usually faster at the beginning of the reaction?

Answer 4

Reaction rates are usually fastest at the start because thats when concentration of the reactants is greatest.

Question 5

How can we monitor reaction rates (other than using a graph)?

Answer 5

We can also monitor reaction rates by measuring changes in the mass or volume of reactants or products.

Question 6

How can we use the measuring of volume to figure out the rate of reaction?

Answer 6

In a reaction, you must look at a gas (or liquid) that is being produced and measure the amount produced. If more gas (or liquid) is produced faster than with other reactants, the rate of reaction is faster because those reactants react faster.

Question 7

How can we use the measuring of mass to figure out the rate of reaction?

Answer 7

In a reaction, you can measure the decrease of mass (as when the reaction takes place, gas may escape from the flask). The decrease of gas will be an indication as to the rate of reaction as a reaction with a high rate of reaction will have a large decrease in mass as a lot of gas has been produced (and escaped) as a result of the reaction.

Question 8

What is activation energy?

Answer 8

The minimum amount of energy needed for a reaction to occur.

Question 9

What is the collision theory?

Answer 9

Chemical reaction can occur only when reacting particles collide with sufficient energy.

Question 10

How are reaction rates increased (involving energy)?

Answer 10

In general, reaction rates are increased when the energy of the collisions is increased, and when the frequency is increased (the number of collisions in a certain amount of time).

Question 11

What four factors affect rate of reaction?

Answer 11

1. Temperature
2. Surface area
3. Pressure
4. Concentration

Question 12

What effect does the increase of temperature have on subatomic particles and the rate of reaction?

Answer 12

Increasing the temperature gives the particles more kinetic energy, so they move faster. This makes the particles collide more frequently.

Question 13

What effect does the increase of surface area have on subatomic particles and the rate of reaction?

Answer 13

Increasing the surface area means more particles are exposed to the reactant. This makes the particles collide more frequently.

Question 14

What effect does the increase of pressure have on subatomic particles and the rate of reaction?

Answer 14

A high pressure means that particles are in a smaller space. This makes the particles collide more frequently. This increases the rate of reaction (Low pressure = low chance of collision, High pressure = high chance of collision).

Question 15

What effect does the increase of concentration have on subatomic particles and the rate of reaction?

Answer 15

A high concentration means more particles in the same space. This makes the particles collide more frequently. This increases the rate of reaction (Low concentration = low chance of collision, High concentration = high chance of collision)

Question 16

What are catalysts?

Answer 16

Substances that speed up chemical reactions (without being permanently changed themselves and without altering the products of the reaction)

Question 17

Why are catalysts used often in industry?

Answer 17

They are used as they make industrial processes more profitable, by making products more quickly, and by allowing reactions to occur at lower temperature, which saves costs.

Question 18

What is a reaction profile?

Answer 18

A diagram to show how the energy stored in substances changes during the course of a chemical reaction.

Question 19

How can reaction profiles be used?

Answer 19

Reaction profiles can be used to show the energy changes for a catalysed and uncatalysed exothermic reaction.

Question 20

How does a catalyst increase the rate of reaction?

Answer 20

The catalyst does not alter the overall energy change. However, since less energy is needed to start the reaction, more reactant molecules have enough energy and so more collisions are successful. This means that the reaction is faster.

Question 21

How are catalysts used in car exhausts?

Answer 21

In catalytic converters in car exhausts, the catalysts are platinum and palladium. There presence lowers the activation energy needed to convert harmful gases into harmless gases. The metals used are expensive but don’t need to be replaced as they are not used up.