Chapter 10

Question 1

What does the RATE of a Chemical Reaction measure?

Answer 1

The rate of a chem reaction measures how fast a reactant is being used up OR how fast a product is being formed.

Question 2

What is the Equation and Units for Rate of Reaction?

Answer 2

rate= change in concentration/time

Units: moldm-3s-1

Question 3

Why is the rate fastest at the beginning of a graph?

Answer 3

Because there is each reactant at its highest concentration.

Question 4

Why does the r.o.r graph begin to level off?

Answer 4

Because the reactants are being used up and the concentration will decrease.

Question 5

Why does the r.o.r graph level off completely?

Answer 5

Because one of the reactants have been completely used up.

Question 6

What does the Collision Theory State and what are the 2 affecting factors?

Answer 6

The Collision Theory states that two reacting particles must collide for a reaction to occur.

1. Collide with the correct orientation.
2. Have sufficient energy to overcome the Activation Energy BARRIER to a reaction.

Question 7

What happens when you increase the concentration and Why?

Answer 7

The rate of reaction will INCREASE because at a higher concentration, there are MORE PARTICLES in a GIVEN VOLUME so the FREQUENCY of SUCCESSFUL collisions will increase the r.o.r as they collide with the correct orientation and sufficient energy to overcome the Ea barrier.

Question 8

What happens when you increase Pressure and Why?

Answer 8

The CONCENTRATION of gas molecules will increase as the SAME NUMBER of gas MOLECULES OCCUPY a SMALLER volume. The molecules are CLOSER together and collide more FREQUENTLY leading to more efficient collisions.

Question 9

How do you find the rates of reaction from a graph?

Answer 9

Draw a tangent and find out the gradients.

Question 10

What is a catalyst?

Answer 10

It is a substance that changes the RATE of a chem reaction WITHOUT undergoing any CHANGE itself.

Question 11

State 3 Facts about Catalysts.

Answer 11

1. They are NOT USED UP in reactions.
2. They REACT with reactants to form an INTERMEDIATE or PROVIDE a SURFACE for the reaction to OCCUR on.
3. At the END of a reaction, they are always REGENERATED.

Question 12

How can you follow a progress of reaction?

Answer 12

You can monitor:
1. Removal of a Reactant - Decrease In Conc.
or
2. Follow the Formation of a Product - Inc in Conc.

Question 13

Whats a Homogeneous Catalyst?

Answer 13

A Homogeneous catalyst has the SAME PHYSICAL state as the reactants. It reacts with the reactants to form an INTERMEDIATE and this then BREAKS DOWN to give PRODUCT then REGENERATES the catalyst.

Question 14

Whats a Hetrogeneous Catalyst?

Answer 14

A Hetrogeneous catalyst has DIFFERENT physical states from the reactants.

Question 15

Describe how Hetrogeneous Catalysts work.

Answer 15

1. The REACTANT molecules form WEAK BONDS with the CATALYST SURFACE. (Adsorption)
2. The BONDS within the REACTANT molecules BREAK.
3. NEW BONDS form and the PRODUCT MOLECULES leave the surface, (Desorption).

Question 16

Give 3 Advantages of using a catalyst.

Answer 16

1. Using a catalyst will PROVIDE an ALTERNATE reaction pathway by LOWERING ACTIVATION ENERGY which will thus LOWER the TEMPERATURE needed for the reaction.
2. Lower TEMP means that LESS ELECTRICITY is needed from COMBUSTION of FOSSIL FUELS.
3. LESS COMBUSTION of FOSSIL FUELS means for a REDUCTION in CO2 emissions.