C8 - Rates of Reaction

Question 1

What is the rate of reaction?

Answer 1

The quanity of product formed over time.

Question 2

How do you measure the rate of reaction?

Answer 2

• How fast a reactant is used up

- How fast the product is made

Question 3

Formula for calculating the rate of reaction

Answer 3

Reactant used or product formed/time take (s)

Question 4

Why is cotton wool placed in the mouth of the flask?

Answer 4

It allows gas out but prevents any materials from being ejected from the flask (if the reaction is vigurous)

Question 5

Why is measuring the rate of reaction from loss in mass not suitable for hydrogen and other gases?

Answer 5

• They have a small relative mass

- Loss in mass may be too small to measure

Question 6

What equipment is used to determine the rate of reaction?

Answer 6

• Gas syringe
• Conical Flask
• Reaction Mixture

Question 7

How do you measure the rate of precipitation?

Answer 7

1) A piece of paper with a black cross on it is placed
2) Add an amount of sodium thiosulphate solution to a conical flask
3) Add the acid and start the timer
4) When looking from above, when the cross dissapears, you stop the timer

Question 8

How does a precipitation reaction form a solid precipitate?

Answer 8

• 2 clear solutions are mixed together
• The precipitae clouds the reaction mixture, so if the piece of paper is placed under a flask with a cross on it, you can see the cross dissapear

Question 9

What are 2 Disadvantages of the Rate of precipitation reaction?

Answer 9

• People may not agree on the exact moment that the cross dissapears
• Only one data point is produced per experiment, so you cant plot a rate reaction graph

Question 10

What does a steeper gradient mean in correlation to the rate of reaction?

Answer 10

The steeper the gradient, the faster the rate of reaction

Question 11

What happens to the reactant if the line is horizontal?

Answer 11

• The reactants are being used up so the line becomes less steep and eventually become horizontal, meaning the reaction has finished

Question 12

How do you find the gradient of a graph

Answer 12

• Drawing a tangent at a curve

- Finding the difference in Y/X

Question 13

What does the curved section of a graph tell us?

Answer 13

The relationship between rate and factor being measure are not directly proportional, so the rate is different at each point

Question 14

What are the 5 factors that affect the rate of reaction?

Answer 14

• Pressure
• Concentration
• Temperature
• Surface area
• Use of a catalyst

Question 15

What happens to the rate of reaction when the concentration is increased?

Answer 15

It also increases

Question 16

How does a catalyst incrwase the rate of reaction?

Answer 16

• It reduces the activation energy

Question 17

What does lowering the activation level do?

Answer 17

• more particles will have enough energy to react when they come together

Question 18

What is collision theory?

Answer 18

when chemical reactions only occur when the reactant particles collid with sufficient energy to react

Question 19

What is the activation energy?

Answer 19

The minimum amount of energy needed

Question 20

What happens if a particle collides with insufficient energy?

Answer 20

They will have unsuccessful collisions and bounce off eachother

Question 21

How would you increases the rate of reaction? (c)

Answer 21

number of successful collisions need to increase

Question 22

How does increasing concentration increase the rate of reaction?

Answer 22

• More reactant particles in a volume so more successful collisions, increasing the rate of reaction

Question 23

How does increasing temperature increase the rate of reaction?

Answer 23

• Particles have more kinetic energy that the required activation energy
• More frequent and successful collisions per second

Question 24

How does increasing the surface area increase the rate of reaction?

Answer 24

• More surface area of the particles are now exposed to the other reactant, making more collisions per second