Rate of reactions

Question 1

How do you work out the rate of a chemical reaction

Answer 1

The quantity of reactant used or product formed / time taken

Question 2

What is the unit for rates of reaction

Answer 2

Grams per cm ³ (g/cm ³)
HT - moles per second (mol/s)
Mass / volume

Question 3

What is a catalyst

Answer 3

A catalyst changes the rate of reaction (speeds it up) but is not used up- it is reusable and produces more of an energy-efficient chemical reaction.

Question 4

What are enzymes

Answer 4

Biological catalysts within the body

Question 5

How do catalysts work?

Answer 5

They provide a different reaction pathway where reactants do not require as much energy to react when they collide. They reduce the required activation energy.

Question 6

In a word equation, what happens if the catalyst is used?

Answer 6

Nothing- it is not shown.

Question 7

What are reversible reactions?

Answer 7

In some chemical reactions, the products can react again to reform the reactants.

Question 8

How do you represent a reversible reaction?

Answer 8

A + B ⇌ C + D

Question 9

What are the directions for a reversible reaction?

Answer 9

A + B Heat —-> C + D
Or
A + B Cool <—— C + D

Question 10

If one direction of a reversible reaction is exothermic.. the opposite direction is?

Answer 10

Endothermic

Question 11

State the four factors affecting rate of reaction

Answer 11

Temperature
Concentration
Surface area
Pressure (of gases)

Question 12

How does temperature affect rate of reactions

Answer 12

The higher the temperature, the quicker the rate of reaction due to more collisions

Question 13

How does concentration affect rates of reaction?

Answer 13

The higher the concentration the quicker the rate of reaction, there is more collisions within the chemicals.

Question 14

How does surface area affect rates of reaction?

Answer 14

The larger the surface area of a reactant solid, the quicker the rate of reaction as there is more space for the particles to move and collide in.

Question 15

How does pressure (of gases) affect the rates of reaction?

Answer 15

When gases react, the higher the pressure upon them, the quicker the rate of reaction.

Question 16

What is collision theory?

Answer 16

Chemical reactions can only occur when reacting particles collide with each other with sufficient energy.

Question 17

How does the temperature affect the rate of collision theory?

Answer 17

Increasing the temperature increases the frequency of collisions and makes the collisions more energetic, therefore increasing the rate of reaction.

Question 18

What is the activation energy?

Answer 18

The minimum amount of energy colliding particles in a reaction need in order to react.

Question 19

How does concentration, pressure (gases) and surface area (solids) affect the rate or collision theory?

Answer 19

Increasing these increases the frequency of collisions, therefore increasing the rate of reaction.