Chapter 10 - Reaction rates and equilibrium

Question 1

What is reaction rate ?

Answer 1

The change in concentration of a reactant or product in a given time

Question 2

What makes an effective collision?

Answer 2

• Particles must have sufficient energy

- Particles must collide in correct orientation

Question 3

Which factors can change the rate of a chemical reaction?

Answer 3

• Concentration and pressure
• Temperature
• Use of a catalyst
• Surface area

Question 4

What effect does increasing temperature have on reaction rate?

Answer 4

Reaction rate increases

Question 5

Explain why increasing temperature has its effect on reaction rate

Answer 5

• Particles have more kinetic energy
• They move at higher speeds
• Collide more frequently
• More successful collisions
• Rate increases

Question 6

What is the rule of thumb for reaction rate and temperature?

Answer 6

A 10C increase in temperature doubles the rate.

Question 7

What effect does increasing concentration/pressure have on reaction rate?

Answer 7

Reaction rate increases

Question 8

Explain why increasing concentration/pressure has its effect on reaction rate

Answer 8

• Concentration increases
• More particles in the same volume
• More frequent collisions
• More successful collisions
• Rate increases

Question 9

How can progress of a chemical reaction be followed ?

Answer 9

• Monitoring the removal of a reactant

- Following the formation of a product

Question 10

What are the two methods of determining reaction rate, when a gas is produced?

Answer 10

• Monitoring the volume of gas produced

- Monitoring the loss of mass of reactants

Question 11

What are the main features of Boltzmann distribution ?

Answer 11

• No molecules have zero energy
• Area under the curve is equal to the number of molecules
• No maximum energy

Question 12

How does a Boltzmann distribution curve change when temperature is increased?

Answer 12

• The peak is lower and shifted to the right

- A greater proportion of molecules can overcome the activation energy

Question 13

How does a Boltzmann distribution show the effect of a catalyst?

Answer 13

• Activation energy with a catalyst is lower than the normal activation energy
• Therefore a greater proportion of molecules exceed the new lower activation energy

Question 14

What is a dynamic equilibrium?

Answer 14

The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentrations do not change.

Question 15

What is Le chateliers principle ?

Answer 15

When a system in dynamic equilibrium is subjected to an external change, the system readjusts itself to minimise the effect of that change.

Question 16

What is said to happen if equilibrium shifts to the right ?

Answer 16

More products are formed

Question 17

What is said to happen if equilibrium shifts to the left ?

Answer 17

More reactants are formed

Question 18

Where does the equilibrium shift if the concentration of the reactants increases ?

Answer 18

Equilibrium shifts to the right

Question 19

Where does the equilibrium shift if the concentration of the products decreases ?

Answer 19

Equilibrium shifts to the right

Question 20

Where does the equilibrium shift if the concentration of the reactants decreases ?

Answer 20

Equilibrium shifts to the left

Question 21

Where does the equilibrium shift if the concentration of the products increases ?

Answer 21

Equilibrium shifts to the left

Question 22

Which reaction investigates the change of position of equilibrium with concentration ?

Answer 22

Chromate ions to dichromate ions

Question 23

What is the colour change from chromate ions to dichromate ions ?

Answer 23

Yellow to orange

Question 24

When the forward reaction is exothermic, what does an increase in temperature do ?

Answer 24

• Position of equilibrium shifts to the left

- More reactants are made

Question 25

When the forward reaction is exothermic, what does a decrease in temperature do ?

Answer 25

• Position of equilibrium shifts to the right

- More products are made

Question 26

When the forward reaction is endothermic, what does an increase in temperature do ?

Answer 26

• Position of equilibrium moves to the right

- More products are made

Question 27

When the forward reaction is endothermic, what does a decrease in temperature do ?

Answer 27

• Position of equilibrium moves to the left

- More reactants are made

Question 28

Which reaction investigates the change of position of equilibrium with concentration ?

Answer 28

Cobalt chloride dissolving in water

Question 29

What is the colour change in the cobalt chloride in water reaction ?

Answer 29

Pink to blue

Question 30

Where does the equilibrium shift if the pressure in the system is increased ?

Answer 30

The equilibrium shifts to the side that has fewer gaseous moles, reducing the pressure of the system

Question 31

Where does the equilibrium shift if the pressure in the system is decreased ?

Answer 31

The equilibrium shifts to the side that has more gaseous moles, increasing the pressure of the system

Question 32

Which reaction investigates the change of position of equilibrium with concentration ?

Answer 32

Nitrogen oxide to nitrogen tetroxide

Question 33

What is the colour change from nitrogen oxide to nitrogen tetroxide ?

Answer 33

Brown to colourless

Question 34

What is the effect of a catalyst on equilibrium?

Answer 34

• Does not change the position

- Speeds up the rates of forward and reverse reactions equally

Question 35

What is different about the equilibrium constant to regular constants ?

Answer 35

• Only constant at a given temperature

- Units change depending on the reaction