Rates of reaction

Question 1

How does the frequency of successful collisions impact the rate of reaction?

Answer 1

a greater frequency of successful collisions causes a greater rate of reaction

Question 2

What two factors must occur for a reaction to happen?

Answer 2

• reactant particles must collide with each other

- the collisions must have enough energy/the activation energy

Question 3

activation energy

Answer 3

minimum energy needed by reactant particles for a reaction to happen

Question 4

successful collision

Answer 4

a collision with the activation energy or more

Question 5

rate of reaction vs reaction time

Answer 5

greater rate of reaction means a lower reaction time

• fast reaction happens in a short time
• slow reaction happens over a long time

Question 6

concentration/pressure and rate of reaction

Answer 6

-rate increases if concentration of a dissolved reactant increases, or if the pressure of a reacting gas increases

-more (gas/liquid) particles in the same volume
(-particles are pushed closer together)
-frequency of successful collisions increases

Question 7

reactant

Answer 7

A substance that reacts together with another substance to form products during a chemical reaction.

Question 8

temperature and rate of reaction

Answer 8

-rate increases if temperature increases

particles gain energy:

• particles move faster
• frequency of collisions increases
• energy of collisions increases, so a greater proportion of collisions are successful

a 10C increases in temperature doubles the reaction rate

Question 9

surface area:volume ratio and rate of reaction

Answer 9

• rate increases when S.A:volume of a solid reactant increases/surface area increases
  (e. g. when lumps are made into a powder)

-more particles of reactant are available
(-more particles exposed on the surface)
-frequency of successful collisions increases

Question 10

rate of reaction

Answer 10

how fast reactants are turned into products

Question 11

why is rate of reaction important in the body

Answer 11

cells need to be supplied with products at a certain rate

if they aren’t the body could be damaged

Question 12

why is rate of reaction important to industry

Answer 12

products make money

products being made at a faster rate decreases money needed to make them and increases profit

Question 13

2 ways to measure rate of reaction

Answer 13

how fast reactants are used up

how fast products are made

Question 14

3 ways to take measurements to determine rate of reaction

Answer 14

• volume of gas given off
• decrease in mass in a reaction that produces gas
• amount of light a cloudy solution lets through

Question 15

4 main factors that affect rate of reaction

Answer 15

surface area

temperature

concentration/pressure

catalysts

Question 16

3 key points to talk about when describing factors that influence the rate of reaction

Answer 16

• (what happens to) particles
• (what happens to the frequency of) collisions
• rate of reaction

Question 17

Marble chips react with hydrochloric acid:
CaCO3(s) + 2HCl(aq) -> CaCl2(aq) + H2O(l) + CO2(g)

State and explain the effect of the following on the rate of reaction:

a) crushing the chips
b) diluting the acid
c) heating the acid

Answer 17

a) rate of reaction increases
surface area:volume ratio increases
frequency of collisions increases

b) rate of reaction decreases
acid particles become less crowded/fewer reactant particles in the same volume
frequency of collisions decreases

c) rate of reaction increases
particles move around faster/have more energy
more collisions have the activation energy
frequency of successful collisions increases

Question 18

Explain, in terms of particles and their collisions, why the mean rate of reaction will differ between different times in the same practical

Answer 18

reactant particles are used up during the reaction

concentration of reactant particles decreases

frequency of collisions decreases

rate of reaction decreases