rates of reaction

Question 1

What are the four things the rate of a reaction depends on?

Answer 1

Temperature
Concentration ( or pressure for gases)
Catalyst
size of particles ( or surface area)

Question 2

Why does a high surface area increase the rate of reaction?

Answer 2

Because there is a larger surface for the particles to collide with one another (or to collide with a catalyst) ,increasing the frequency of collisions and the likely hood of sucessful collisions.

Question 3

Define collision theory

Answer 3

For a chemical reaction to occur, the reactant particles must collide and with enough energy for the collision to be succesful.

Question 4

How does an increase in temperature affect the rate of reaction ?

Answer 4

It increases it because ff the particles have a higher temperature they have more and energy and so collide more often and are more likelly to have succesfull collisions.

Question 5

How does a higher conc/ pressure affect the rate of reaction ?

Answer 5

If a solution is more concentrated it means there are more particles in the same volume so the frequency of collisions increases. Similarly, if a gas has a higher pressure then the particles are closer together.

Question 6

why break up a solid reactant

Answer 6

if a solid reactant is broken up into pieces it’s surface area will increase, this means the particles around it in thr solution have more area to work on.

Question 7

how do catalysts effect the rate of reaction?

Answer 7

a solid catalyst works by giving reacting particles a surface area to stick to. they increase the number of successful collisions by offering a reaction pathway with a lower activation energy.

Question 8

describe a rates of reaction experiment that involves a change in mass

Answer 8

this works only for a reactions where a gas is given off. place you flask containing your solution on scales. As the gas is released the mass disappearing is easily measured on the scales. The quicker the reading on the balance drops the faster the rate of reaction.

Question 9

equation for rate of reaction

Answer 9

rate of reaction = amount of reactant used or amount of product formed/ time

Question 10

describe a rate of reaction experiment that involves a cloudy percipitate.

Answer 10

this is used when the product of the reaction forms a cloudy percipitate which clouds the solution. observe a marker throught the solution and see how long it takes to disappear. The quicker the marker disappears, the quicker the reaction.

Question 11

how might out observe the effect of a catalyst on the rates of reaction?

Answer 11

meausure the rates of reaction for two solutions of exactly the same concentration, temperature and surface area of reactant, only one is reacted with a catalyst.

Question 12

testing the effect of surface area

Answer 12

repeat identical experiments only with the reactant more crushed up each time. the finer the reactant is ground the faster the rate of reaction will be.

Question 13

Describe an expriement for volume of gas given off.

Answer 13

This method uses a gas syringe to measure the volume of gas given off. The more gas given off during a given time interval, the faster the rate of reaction. Gas syringes are extremely accurate.

Question 14

reaction of hydrochloric acid and marble chips - What it is often used for?

Answer 14

The effect of breaking up the solid reactant into smaller bits

Question 15

How would you change the marble chips? what would you keep the same?

Answer 15

keep the mass of marble chips the same. Each time have it more crunched up.

Question 16

What is a good experiement for measuring the effect of concentration?

Answer 16

Magnesium and dilute hydrochloric acid.

Question 17

Describe the magnesium and hydrochloric acid reaction

Answer 17

Hydrogen gas is given off which can be measured on a mass balance. (or a gas syringe). The change of the rate at which this happens can be observed by altering the concentration of hydrochlorci acid

Question 18

What is a good experiement for demonstrating cloudy precipiates?

Answer 18

Sodium thiosulfate and HCl produce a cloudy precipitate

Question 19

What does the sodium thiosulfate reaction involve?
what must be kept the same?
what do you change to observe the rate of reaction?

Answer 19

Watching a black marker disappear through the cloudy sulfur precipiate formed. the depth of the liquid must be kept the same
The temperature ( this is difficult to do accurately)

Question 20

What will the results of the sodium thiosulfate reaction show?

Answer 20

The higher the temperature, the quicker the rate of reaction will be therefore the black marker will dissapear faster.

Question 21

What can the sodium thiosulfate reaction also be used to test for?

Answer 21

the affect of concentration. (changing the concentration of the hydrochloric acid)

Question 22

What is a good reaction for showing the effect of different catalysts?

Answer 22

The decomposition of hydrogen peroxide.

Question 23

What is the chemical equation for hydrogen peroxide reaction

Answer 23

2H2O2(aq) -> 2H20(l) + O2(g)

Question 24

What is the catalyst for the hydrogen peroxide reaction?

Answer 24

manganease oxide

Question 25

What do you use to measure the rate of reaction in hydrogen peroxide reaction? Why?

Answer 25

gas syringe because oxygen gas is given off.

Question 26

What else can the hydrogen peroxide reaction be used to test for?

Answer 26

The effect of concentration or temperature.

Question 27

Why are reactions faster at the beginning of the graph

Answer 27

Because the dissolved reactant has a great concentration

Question 28

What does it mean when the rate of reaction graph has flattened out?

Answer 28

The reaction is completed