Chemsitry TOPIC 7

Question 1

what is meant by rate of reaction?

Answer 1

how fast reactants turn into products

Question 2

how can you tell how fast a reaction is from a graph?

Answer 2

the steeper the line , the higher rate of reaction

Question 3

what is activation energy?

Answer 3

the minimum amount of energy needed for reactants to start forming products.

Question 4

the factors affecting rate of reaction?

Answer 4

• temperature
• surface area
• concentration of a solution / pressure of a gas
• the presence of a catalyst

Question 5

how does increased temperature increase the rate of reaction?

Answer 5

• the particles have more kinetic energy so move faster and collide with more force
• this means more energy for the reaction because there are more frequent, successful collisions
• and the products are created at a faster rate

Question 6

how does increased surface area increase the rate of reaction?

Answer 6

• there are more collisions if there is more area for particles to hit each other
• this means more energy for the reaction due to frequent , successful collisions
• the products are created at a faster rate

Question 7

how does increased concentration/ pressure increase the rate of reaction?

Answer 7

• there are more particles that have potential to collide with one another
• therefore more frequent successful collisions provide energy for the reaction
• and products are obtained at a higher rate

Question 8

how does the use of a catalyst increase the rate of reaction?

Answer 8

• the catalyst is able to speed up the rate of reaction via other routes
• meaning the amount of activation energy is lowered so the reactants turn into products at a faster rate

Question 9

what is the definition of a catalyst?

Answer 9

a substance that speeds up the rate of reaction without being used up or changed.

Question 10

equation for rate of reaction?

Answer 10

rate of reaction = amount of reactants used up OR amount of product formed / time taken

Question 11

the 3 ways to measure rate of reaction:

Answer 11

• percipitation /change of colour (visual change)
• change in mass (mas can decrease if gas is produced/ reactants react with the air)
• the volume of a gas given off ( the gas can be measured in a syringe)

Question 12

equation for OVERALL ENERGY CHANGE?

Answer 12

overall energy change = energy of reactants - energy of products

Question 13

is breaking bonds exothermic or endothermic?

Answer 13

endothermic , because to break bonds it requires energy from its surroundings

Question 14

define a bond energy.

Answer 14

amount of energy needed to break one mole of a particular covalent bond.

Question 15

is forming bonds exothermic or endothermic?

Answer 15

exothermic , because it would release energy to its surroundings