Reactions

Question 1

Does endothermic release or take in heat from the surroundings?

Answer 1

Takes in heat

Question 2

Does exothermic take in heat or give off heat to/from the surroundings

Answer 2

Gives off heat

Question 3

Reaction profile diagram for exothermic explained:

Answer 3

More energy is stored in the bonds of the reactants than the products

Question 4

Reaction profile for an endothermic reaction explained:

Answer 4

More energy is stored in the bonds of the products than the reactants

Question 5

Examples off applications of an exothermic reaction

Answer 5

Combustion, respiration, metals and acids

Question 6

Examples of applications of endothermic reactions:

Answer 6

Thermal decomposition, Photosynthesis

Question 7

In an exothermic reaction will the temperature rise or not

Answer 7

Yes the temp of the reaction will go up

Question 8

In an endothermic reaction will the temp go up or not

Answer 8

No temperature will decrease

Question 9

What happens if you add a catalyst to the reaction

Answer 9

The catalyst will lower the activation energy in order to speed up the reaction

Question 10

In an exothermic reaction are bonds made or broken

Answer 10

Made (MEXican)

Question 11

In an endothermic reaction are bonds made or broken

Answer 11

Broken (BENdy)

Question 12

What is the energy needed to break 1mole of a covalent bond in a molecule called

Answer 12

BOND ENERGY (kJ/mol)

Question 13

How can we work out wether a reaction is endothermic or exothermic without measuring temp change

Answer 13

BENDY MEXICAN (calculating wether bonds are made or broken)

Question 14

Method to calculate wether the reaction is endothermic or exothermic

Answer 14

1. Calculate energy in (bonds broken)
2. Calculate energy out (bonds made)
3. Calculate the overall energy change (energy in - energy out)
4. If the value is negative it is EXOTHERMIC and if the value is positive it is ENDOTHERMIC

Question 15

What is needed for a reaction to happen

Answer 15

Reactant particles must collide with each other with a minimum of activation energy. Successful collisions have the activation energy or more

Question 16

How does a change in temperature affect the rate of a reaction

Answer 16

Increases when temperature increases because particles gain energy and move faster.
Allows the frequency of collisions to increase and so a greater proportion of these are successful

Question 17

How does the change in concentration and pressure affect the rate of a reaction

Answer 17

Increases if the concentration of a dissolved reactant increases OR if the pressure of a reacting gas increases
There are more particles in the same volume so the frequency of successful collisions increases

Question 18

How does a change in surface area to volume ratio affect the rate of a reaction

Answer 18

Increases when the surface area:volume ratio of a solid reactant increases e.g. when lumps are made into powder
More particles of reactant are available so the frequency of successful conditions increases

Question 19

What is a catalyst

Answer 19

A substance that speeds up the rate of reaction without being used up in the process or altering the products of the reaction

Question 20

Give an example of a biological catalyst and what is it used for

Answer 20

Enzymes
Used in the production of alcoholic drinks

Question 21

What does activation energy mean

Answer 21

The minimum amount of energy requires for a successful collision (reaction) to take place