Rates And Energy

Question 1

How can the rate of reaction be found?

Answer 1

Measuring the amount of reactant used, or how much of a product is formed, and the time taken.
Also you can measure the time taken for a certain amount of solid or gas to appear in a solution.

Question 2

Rate of reaction equation

Answer 2

Rate of reaction = amount of reactant used/time

Or

Rate of reaction = amount of product formed/time

Question 3

On a graph with product or reactant against time, how can a rate of reaction be found at any given time?

Answer 3

The gradient. The steeper the gradient, the faster the reaction is at that time.

Question 4

What does the collision theory state?

Answer 4

That reactions can only happen if particles collide. However colliding isn’t enough as there must be enough energy to change into new substances.

Question 5

What is the minimum energy that it needed for a reactions?

Answer 5

The activation energy

Question 6

What factors increase the chance of collisions or the energy of the particles?

Answer 6

Temperature
Concentration of solutions
Pressure of gases
Surface area of solids
Using a catalyst

Question 7

Why are smaller pieces with the same mass better than large pieces for a reaction?

Answer 7

Smaller pieces have a larger surface area, more area exposed. This means there will be more collisions in the same time, so the rate of reaction increases?

Question 8

What happens to a rate of reaction when the temperature is increased?

Answer 8

With an increased temperature the speed of the particles increases because they have gained more kinetic energy. This means they will collide more often and this increases the rate of reaction.

Question 9

If there was a rise or fall of even 10 degrees C, how much will the rate of reaction increase or decrease?

Answer 9

It will double.

Question 10

What happens to a rate of reaction if the concentration of a solution increases?

Answer 10

This means there are more particles dissolved in the same volume, which means more collisions. This then increases the rate of reaction.

Question 11

What happens to a rate of reaction if the pressure of a gas increases?

Answer 11

This means that more gas molecules are out into the same volume so they collide more frequently which increases the rate of reactions.

Question 12

What is a catalyst?

Answer 12

A substance that changes the speed of a reaction but is not changed itself. It isn’t fully used up so at the end of a reaction, it can be collected and used again.

Question 13

How do catalysts speed up a reaction?

Answer 13

They lower the activation energy so that more collisions occur.

Question 14

In what form can catalysts be in to make them more effective?

Answer 14

They are solids that have large surface areas.

Question 15

Why do different reactions need different catalysts?

Answer 15

Catalysts often work with only one type of reaction.

Question 16

Why are catalysts used in many industrial processes?

Answer 16

They can be expensive but they can be economical because they can be reused. Also it means that the catalysts reduce the activation energy and time needed for reactions. This means costs and environmental impacts are reduced. It can also conserve resources like fossil fuels.

Question 17

How can some catalysts cause harm if they get into the environment?

Answer 17

Many of the catalysts used industry involve transition metals and their compound which can be toxic.

Question 18

What can offer more development of catalysts?

Answer 18

Nanoscience can help find better and more efficient catalysts.
Also enzymes which are biological catalysts cans be used to also reduce energy costs.

Question 19

What are exothermic reactions?

Answer 19

Reactions that transfer energy to the surroundings.

Question 20

What are examples of exothermic reactions?

Answer 20

Combustion, such as burning fuels
Oxidation reactions such as respiration
Neutralisation reactions involving acids and bases.

Question 21

What are endothermic reactions?

Answer 21

Reactions that take in energy from the surroundings.

Question 22

What is an example of an endothermic reaction?

Answer 22

Thermal decomposition reactions need to be heated continuously to keep the reaction going.

Question 23

In a reversible reaction if one direction is exothermic, what is the other direction?

Answer 23

Endothermic. It would keep reversing

Question 24

What is the difference between the energy released in an exothermic reaction and the energy taken in in an endothermic reaction, in a reversible reaction?

Answer 24

There is no difference, they are equal.

Question 25

What does the rate of reaction measure?

Answer 25

The speed of a reaction.