RATE OF REACTION

Question 1

Mean rate of reaction =

Answer 1

Quantity of reactant used/ time taken

Question 2

Quantity of reactant used/ time taken =

Answer 2

Mean rate of reaction

Question 3

Factors that affect rates of reaction

Answer 3

The concentration of reactants in solution
The pressure of reacting gasses 
The surface area of solid reactants 
The temperature 
The presence of a catalyst

Question 4

Explain collision theory LEARN OBH

Answer 4

Chemical reactions can occur only when reacting particles COLLIDE with each other AND with SUFFICIENT ENERGY. The MINIMUM amount of ENERGY that particles must have to react is called the ACTIVATION ENERGY

Question 5

What happens when you increase the concentration in a solution?

Answer 5

It increases the frequency of collisions, and so increases the rate of reaction

Question 6

What happens when you increase the pressure of reacting gases?

Answer 6

It will increase the frequency of collisions, and so increases the rate of reaction

Question 7

What happens when you increase the surface area of solid reactants?

Answer 7

It increases the frequency of collisions, and so increases the rate of reaction

Question 8

What happens when you increase the temperature in a reaction?

Answer 8

The frequency of collisions increases so they become for energetic and as a result the rate of reaction increases

Question 9

What is a catalyst and how does it affect the rate of reaction?

Answer 9

Catalysts SPEED up the rate of reaction WITHOUT ALTERING THE PRODUCTS of the reaction, being itself UNCHANGED CHEMICALLY IN MASS at the end of the reaction

The catalyst is still there, unchanged, at the end of the reaction.

Question 10

What is an enzyme and how does it affect the rate of reaction?

Answer 10

Enzymes are biological catalysts. Enzymes are used in the production of alcoholic drinks by fermentation.

Question 11

Changes in heat energy accompany the following changes:

Answer 11

Salts dissolving in water
Neutralisation réactions
Displacement reactions
Precipitation reactions

Question 12

What happens to energy is chemical reactions?

Answer 12

Energy is CONSERVED in chemical reactions. The amount of energy in the universe AT THE END of a chemical reaction IS THE SAME AS BEFORE the reaction takes place.

Question 13

Exothermic reactions

Answer 13

Exothermic reactions s one that TRANSFERS ENERGY to the surroundings so the temperature is the surroundings INCREASES

Question 14

Endothermic reactions

Answer 14

An endothermic reaction is one that takes energy from the surroundings so the temperature of the surroundings DECREASES

Question 15

Examples of endothermic reactions

Answer 15

Thermal decomposition

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Question 16

Nreaking bonds is

Answer 16

Endothermic

Question 17

Making bonds is

Answer 17

Exothermic

Question 18

Exothermic heat energy change

Answer 18

Is more heat is released in forming bonds in the products than is required to break bonds in thé reactants

Question 19

Endothermic heat energy change

Answer 19

If less heat is released in forming the bonds in the products than is required in breaking bonds in the reactants

Question 20

During a chemical reaction

Answer 20

Energy must be supplied to BREAK BONDS in the reactants

Energy is released to FORM BONDS in the products

Question 21

Overall energy change =

Answer 21

Energy needed to break the bonds - energy released as bonds are made

Question 22

Energy needed to break the bonds - energy released as bonds are made =

Answer 22

Overall energy change

Question 23

Exothermic reaction calculation

Answer 23

The sum of the difference between the calculations is NEGATIVE

Question 24

Endothermic reaction calculation

Answer 24

The difference between the calculations is positive.

Question 25

Reaction profiles

Answer 25

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

The MINIMUM amount of energy that particles must have to react is called the ACTIVATION ENERGY