Rate Of Reaction

Question 1

Collision theory

Answer 1

The collision theory states that the rate of a chemical reaction is directly proportional to the frequency of effective collisions.

Question 2

Rate of reaction

Answer 2

The amount of products formed per unit time/ the amount of reactants used up per unit time

Question 3

Change in Mass:

How will the mass of the content change over time?

Answer 3

[Gas ] will escape into the atmosphere, resulting in a loss of mass

Question 4

Change in Mass:

How can the rate of reaction be calculated?

Answer 4

Plot a graph of mass of reaction mixture against time, gradient of the graph represent the rate of reaction at that point in time.

Question 5

Measuring Change in Volume

Answer 5

Measure Volume of gas given off at regular time intervals using a gas syringe.

Question 6

Factors affecting rate of reaction

Answer 6

Concentration, Pressure, Particle Size, Temperature, Presence of catalyst

Question 7

Effect of concentration

Answer 7

When concentration of solution increases, the number of reactant particles per unit volume increases, increasing the frequency of effective collisions between the reactant particles, hence rate of reaction is faster.

Question 8

Effect of pressure

Answer 8

As pressure of gas increases, reactant gas particles are forced closer, increasing the number of gaseous particles per unit volume, increasing the frequency of effective collision between the gaseous particles. Hence, the rate of reaction is faster.

Question 9

Effect of Particle Size

Answer 9

As particle size decreases, there is a greater surface area for reacting particles to collide, increasing the frequency of effective collisions between the reactant particles. Hence, the rate of reaction is faster.

Question 10

Effect of Temperature

Answer 10

As temperature increases, particles gain kinetic energy and move faster. As a result, there will be a higher proportion of particles having energy greater than or equal to activation energy, increasing the frequency of effective collisions between particles. Hence, the rate of reaction is faster.

Question 11

Catalyst

Answer 11

A substance which increases the rate of a chemical reaction with itself remaining chemically unchanged at the end of the reaction.

Question 12

Characteristics of a catalyst

Answer 12

1. Changes the rate but not the yield of the chemical reaction
2. Only a small amount is needed to change the rate of reaction.
3. Not used up in the chemical reaction.
4. Selective in its action. Different catalysts speed up specific chemical reactions.

Question 13

Effect of a catalyst

Answer 13

A catalyst provides an alternative reaction pathway of lower activation energy,increases the proportion of particles having energy greater than or equals to the activation energy, increasing the frequency of effective collisions between the particles, hence rate of reaction is faster.

Question 14

Use of catalyst

Answer 14

Iron- Ammonia
Platinum/ Rhodium- Catalytic converters
Aluminium oxide/ Silicone dioxide- production of hydrogen in cracking process

Question 15

Enzymes

Answer 15

Biological catalyst that alter the rate of chemical reactions in plants and animals.

Question 16

Characteristics of enzymes

Answer 16

1. Protein in nature.
2. Highly specific in their actions.
3. Sensitive to temperature change. (Inactive if low temperature, denature if high temperature)
4. Sensitive to pH changes.

Question 17

Use of Enzymes

Answer 17

1. Manufacture of wine

2. Biological washing powder