Rates of Reaction

Question 1

What is a rate of chemical reaction?

Answer 1

How fast reactants are changed into products?

Question 2

Give examples of a slow, moderate speed and fast reaction

Answer 2

Slow - rusting
Moderate speed - Magnesium+ acid
Fast - burning / explosions

Question 3

How can you calculate the speed of a reaction?

Answer 3

Amount of product formed/used
—-—————————-
Time

Question 4

On a graph, the steeper the line, the faster the rate of reaction. Overtime the line becomes less steep what does this indicate?

Answer 4

The reactants are used up

Question 5

What is the collision theory?

Answer 5

Particles must collide with enough energy in order to react.

Question 6

What is collision frequency?

Answer 6

How often the particles collide. The more collisions there are, the faster the reaction.

Question 7

What is the rate of chemical reaction dependent on?

Answer 7

Collision frequency
Energy transferred during a collision

Question 8

What is the minimum amount of energy that particles need to react called?

Answer 8

Activation energy

Question 9

Why do particles need activation energy?

Answer 9

To break the bonds in order to react and start the reaction

Question 10

What factors increase the number of collisions in a reaction?

Answer 10

The amount of energy particles that collide. An increase in the number of collisions increases the rate of reaction

Question 11

Name four things that affect the rate of reaction

Answer 11

1) Temperature
2) Concentration of a solution/pressure of gas
3) Surface area
4)Presents of a catalyst

Question 12

What happens when the temperature is increased in a reaction?

Answer 12

When the temperature is increased, the particles have more energy and move faster so have more collisions.

Question 13

What happens when the concentration or pressure is increased in a reaction?

Answer 13

If a solution/gas is more concentrated, it means there are more particles of reactant in the same volume so collisions are more likely so the reaction rate increases

Question 14

What happens when the surface area is increased in a reaction?

Answer 14

The rate of reaction increases if one reactant is solid and breaks into smaller pieces therefore increases its surface area so the surface area to volume ratio is increased

Question 15

What is the calculation for measuring the rate of a reaction?

Answer 15

Question 16

Name three different ways that the rate of reaction can be measured

Answer 16

1) precipitation
2) change in mass
3) volume of gas given off

Question 17

Explain how a rate of reaction can be measured through precipitation

Answer 17

1) mix two see through solutions in a flask
2) Put the flask on a piece of paper that has a mark on it
3) observe the mark through the mixture and measure how long it takes for the mark to be obscured. The faster the mark disappears, the faster the reaction.

Question 18

What is the potential problem with measuring a rate of reaction through precipitation?

Answer 18

The result is subjective - different people might not agree on exactly when the mark disappears

Question 19

Explain how to measure the rate of reaction through the change in mass

Answer 19

1) mix two solutions in a flask.
2) put the flask on a mass balance and take a reading
3) You know the reaction has finished when the reading on the balance stop changing
4) you can plot a graph of change in mass against time

Question 20

Explain how to measure the rate of reaction through the volume of gas given off

Answer 20

1) mix two solutions in a flask and attach a gas syringe
2) measure the amount of gas given off at set time intervals
3) you can tell the reaction is finished when no more gas is produced
4) you can plot a graph of gas volume against time elapsed

Question 21

How can you measure how surface area affects the rate of reaction?

Answer 21

1) add marble chips CaCO3 and dilute HCl to a flask
2) add a gas syringe
3) measure the volume of gas (CO2) produced at regular intervals
4) plot the results on a graph - time on x axis and volume on y axis
5) repeat the experiment but this time with the marble chips more crunched up

Question 22

Finer particles of a solid in a rate of reaction experiment means a ________ rate

Answer 22

Higher

Question 23

Give examples catalysts which can be used to speed up a rate of reaction experiment

Answer 23

Manganese (IV) oxide MnO2
Copper (II) oxide CuO
Zinc oxide ZnO