3.b - Rates of reaction

Question 1

how does a change in concentration of a solution ( or pressure ) effect the rate of reaction

Answer 1

increased concentration ( pressure) = increased rate of reaction

Question 2

why does an increased concentration ( or pressure )= increased rate of reaction ( collision theory)

Answer 2

more concentrated ( or higher pressure) = more particles in same volume ( a lot of particles in smaller amount of space) = more successful collisions are likely to happen= increase collision frequency = increase in rate

Question 3

describe an experiment used to investigate the effects of changes in concentration of a solutions on the rate of reaction

(eg using marble chips and dilute hydrochloric acid)

Answer 3

1. set up apparatus- conical flask with bung and tube connected to a gas syringe
2. conical flask contains marble chips and HCL ( gives off CO2 gas)
3. measure volume of gas produced using a gas syringe
4. take readings at regular time intervals + record results in a table
5. use results to plot graph
6. repeat experiment with exactly the same volume of acid, the same mass or marble chips, same surface area of marble chips but a different concentration of acid
7. carry on repeating with different strengths of concentration of acid

Question 4

describe an experiment to investigate the effects of changes in surface area of a solid

( using marble chips + hydrochloric acid )

Answer 4

1. . set up apparatus- conical flask with bung and tube connected to a gas syringe
2. conical flask contains marble chips and HCL ( gives off CO2 gas)
3. measure volume of gas produced using a gas syringe
4. take readings at regular time intervals + record results in a table
5. use results to plot graph
6. repeat experiment with exactly the same volume of acid, the same mass of marble chips , same concentration of acid but with marble more crunched up
7. then repeat with same mass of powdered chalk

Question 5

describe an experiment to investigate the effects of changes in temperature

( using sodium thiosulphate + hydrochloric acid ( both clear solutions = yellow precipitate of sulphur )

Answer 5

1. sodium thiosulphate + hydrochloric acid ( both clear solutions) = yellow precipitate of sulphur
2. measure rate by timing how long it take for black cross to disappear ( cos of yellow cloudy sulphur )
3. repeat with reaction with solutions at different temps ( using water bath )
4. depth / volume of liquid must be kept the same
5. results = higher temp = quicker reaction= less time for black cross to disappear

Question 6

describe an experiment to investigate the effects of changes in the use of a catalyst

( decomposition of hydrogen peroxide )

Answer 6

decomposition of hydrogen peroxide ( normally a slow reaction) sped up by catalysts eg. manganese oxide , copper oxide , zinc oxide

1. . set up apparatus- conical flask with bung and tube connected to a gas syringe
2. conical flask contains hydrogen peroxide and catalyst ( gives off oxygen, O2 gas)
3. measure volume of gas produced using a gas syringe
4. take readings at regular time intervals + record results in a table
5. repeat experiment with same volume + concentration of hydrogen peroxide but different catalyst ( mass of catalyst must be kept the same )

Question 7

how does a change in surface area of a solid effect the rate of reaction

Answer 7

increased surface area ( smaller solid particles eg. crushed) = increased rate of reaction

Question 8

why does an increased surface area = increased rate of reaction ( collision theory)

Answer 8

increases SA to volume ratio = particles around solid have more area to work on = increase collision frequency = increase in rate

Question 9

how does a change in temperature of a solid effect the rate of reaction

Answer 9

increased temperature = increased rate of reaction

Question 10

why does an increased temperature = increased rate of reaction ( collision theory)

Answer 10

increase temp= particles have more energy = particles move faster = more successful collisions ( particles collide with enough energy to react ) = increase collision frequency = increase rate

Question 11

how does a change in use of a catalyst effect the rate of reaction

Answer 11

catalyst used = increased rate of reaction

Question 12

definition of catalyst

Answer 12

substance that increase rate of reaction but is not chemically changed ( chemically unchanged ) at the end of the reaction

Question 13

how does a catalyst work

Answer 13

provides an alternative pathway with lower activation energy

Question 14

PAPER 2

draw + explain reaction profile diagrams showing /\H and activation energy with and with out catalyst

Answer 14

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