Unit 3: rates of reaction

Question 1

Name three ways to measure the rate of reaction

Answer 1

1. Measuring a volume of gas given off
2. Measuring a change in mass
3. Measuring a solid disappearing/appearing

Question 2

How do you calculate rate of reaction?

Answer 2

rate of reaction = change in product / time

Question 3

What is collision theory?

Answer 3

Collision theory states that particles must collide with a certain amount of energy before they can react.

Question 4

What is activation energy?

Answer 4

The minimum energy particles need to react.

Question 5

What does the start of a rate of reaction graph show? (If its the steepest part)

Answer 5

It is the fastest part of the reaction. The concentration of reactants is high so lots of collisions are successful)

Question 6

What does the middle of a rate of reaction graph show? (if its a bit less steep)

Answer 6

The reaction is slowing down. Some of the reactants have turned into products so not all collisions are between reactants.

Question 7

What does the end of a rate of reaction graph show? (if the line is flat)

Answer 7

the reaction has stopped. One the the reactants has been used up – the concentration of this reactant is 0 so the reaction stops as there can be no more successful collisions.

Question 8

What are the three main factors that affect rate of reaction?

Answer 8

1. Surface area
2. Concentration
3. Temperature

Question 9

Why does increasing surface area of reactants increase the rate of reaction?

Answer 9

Smaller pieces of a reactant have a larger surface area than larger pieces. This means more contact is possible between particles of the two reactants, which will lead to more frequent collisions and therefore more successful collisions.

Question 10

Why does increasing concentration of a reactant increase the rate of reaction?

Answer 10

A higher concentration means there will be more particles of that reactant in a given volume, which will lead to more frequent collisions and therefore more successful collisions.

Question 11

Why does increasing temperature increase the rate of reaction? (two reasons)

Answer 11

at a higher temperature, the particles have more energy so they move around faster. This leads to more frequent collisions, therefore more successful collisions.

Also, more particles have enough energy (more than activation energy) to react, so a higher proportion of collisions will be successful.

Question 12

What is one extra way you could speed up the rate of reaction?

Answer 12

Using a catalyst.

Question 13

What is the law of conservation mass?

Answer 13

The law of conservation mass states that no atoms are lost or made during a chemical reaction.