Paper 2 (6)

Question 1

What does the rate of chemical reaction refer to?

Answer 1

The speed at which the reactants get turned into products

Question 2

Give an example of a slow reaction

Answer 2

-> Rusting of iron

Question 3

Give an example of a typical rate of reaction

Answer 3

Magnesium and acid produces a gentle stream of hydrogen bubbles

Question 4

Give an example of a fast reaction

Answer 4

Explosions such as fireworks

Question 5

To measure the rate of a reaction, we can either measure…

Answer 5

-> How fast the reactants are being used up
OR
-> How fast the products are being formed.

Question 6

What are the two equations to work out rate of reaction?

Answer 6

Rate of reaction = quantity of reactants used/ time taken
OR
Rate of reaction = quantity of products formed/ time taken

cm3/s
g/min

Question 7

Name four factors that affect the rate of chemical reactions.

Answer 7

Temperature
Concentration/ pressure
Surface Area
Catalyst

Question 8

What does the collision theory state?

Answer 8

Collision theory states that for particles to react, they have to collide with sufficient energy.

Question 9

The minimum amount of energy required for a reaction to take place is called the _________ energy.

Answer 9

Activation

Question 10

When considering how a condition will affect the rate of reaction, you have to consider how it will affect the _________ of collisions, and/or the _________ of the particles.

Answer 10

frequency
energy

Question 11

Explain how the rate of reaction changes with increasing temperature.
4 points

Answer 11

As temperature increases the particles gain kinetic energy, and so move around more quickly. This means that they collide more frequently, and with more energy. Therefore, there will be more collisions that surpass the activation energy, so the rate of reaction will increase.

Particles will have more energy
Particles will collide more frequently
More successful collisions
Higher rate of reaction

Question 12

What does concentration/ pressure refer to?

Answer 12

Particles per unit of volume.

Concentration = generally solutions
Pressure = gases

Question 13

What increases the frequency of collisions of the particles in a reaction? Give 2

Answer 13

Increasing the concentration
Increasing the temperature
Using powder instead of small chunks

Question 14

A substance that increases the rate of a reaction without being chemically changed, or used up, is called a _________.

Answer 14

catalyst

Question 15

What do catalysts do to the reaction energy?

Answer 15

Lowers the activation energy by providing an alternative reaction pathway.
Higher proportion of successful collisions.

Question 16

Give three examples of catalysts:

Answer 16

Cobalt
Nickel
Enzymes

Question 17

Should you include the catalyst in the chemical reaction as one of the reactants?

Answer 17

No

Question 18

Do transition metals make good catalysts?

Answer 18

Yes

Question 19

What is the equation to calculate the gradient?

Answer 19

change in y over change in x
(rise over run)

Question 20

By finding the gradient of the tangent to a curve at a specific time, we can calculate the:

Answer 20

Rate of reaction at a specific time

Question 21

During a chemical reaction, when is the rate normally fastest?

Answer 21

At the start

Question 22

A line may be steepest at the start of a reaction because there are a lot of _________.
Over time, the line may become ____ steep as the reactants are _____ up.
At the end of the reaction, when all the reactants have been used up, the line p_______.

Answer 22

reactants
less
used
plateaus

Question 23

You may sometimes hear the term d______ equilibrium rather than just equilibrium. They both mean the same thing, so you can use either.

Answer 23

dynamic

Question 24

What is the correct symbol for a reversible reaction?

Answer 24

⇌

Question 25

What is a reversible reaction?

Answer 25

A reversible reaction is one in which both the forward and reverse reactions can take place.

Question 26

Give 2 statements about a system in equilibrium:

Answer 26

-> It requires a closed system
-> The concentrations of the reactants and products remain constant
-> The forward and backward reactions occur at the same rate

Question 27

At equilibrium, if the concentration of reactants is higher than the concentration of products, we say that the position of equilibrium lies to the:

Answer 27

Left

Question 28

What happens in an endothermic reaction?

Answer 28

Heat energy is taken in from the surroundings

Question 29

In a reversible reaction, if the forward reaction is exothermic, the backward reaction is ___________.

Answer 29

endothermic

Question 30

If the position of equilibrium lies to the right, it means there are more:

Answer 30

Products

Question 31

In a reversible reaction, if the forward reaction is endothermic, what would be the affect of increasing the temperature?

Answer 31

Equilibrium would shift to the right

Question 32

In a reversible reaction, if the forward reaction is exothermic, what would be the effect of decreasing the temperature?

Answer 32

Yield of products would increase

Question 33

What is Le Chatelier’s Principle?

Answer 33

Le Chatelier’s principle states that if you change the conditions of a reversible reaction, the position of equilibrium will shift to try and counteract the change.

Question 34

At equilibrium, if there are more products than reactants, we say that the position of equilibrium lies:

Answer 34

To the right

Question 35

What are the three factors that affect the position of equilibrium?

Answer 35

Temperature
Concentration
Pressure

Question 36

An increase in pressure moves the position of equilibrium to whichever side has the:

Answer 36

smaller number of gas molecules.

Le Chatalier’s principle states that if pressure is increased, equilibrium will shift to decrease the pressure. This means that equilibrium will shift to the side with less moles of gas as these will contribute less pressure.

Question 37

In a reversible reaction, changes in pressure will only affect substances that are in the:

Answer 37

gaseous state

Question 38

Le Chatalier’s principle states that if you increase the pressure, the position of equilibrium will shift to the side that _________ the pressure back down.

Answer 38

decreases

Question 39

N2(g) + 3H2(g) ⇋ 2NH3(g)
In the above reaction, increasing the pressure will:

Answer 39

Shift the position of equilibrium to the right.

Question 40

H2(g) + I2(g) ⇋ 2HI(g)
In the above reaction, increasing the pressure will:

Answer 40

Have no effect on the position of equilibrium

Question 41

2NO2(g) ⇋ N2O4(g) (-24 kJ mol-1)

In the reaction above, the (-24 kJ mol-1) tells us that the forward reaction is:

Answer 41

Exothermic

Question 42

2NO2(g) ⇋ N2O4(g) (-24 kJ mol-1)
In the above reaction, increasing the temperature will:

Answer 42

Shift the position of equilibrium to the left.
Le Chatalier’s principle states that if you increase the temperature, the position of equilibrium will shift to reduce the temperature. This means equilibrium will shift in the endothermic direction, which in this case is to the left.

Question 43

N2(g) + 3H2(g) ⇋ 2NH3(g)
For the above reaction, increasing the concentration of nitrogen will:

Answer 43

Shift the position of equilibrium to the right.
Le Chatalier’s principle states that if you increase the concentration of a substance, the position of equilibrium will shift to reduce the concentration back down. This means that if you increase the concentration of nitrogen, equilibrium will shift to the right so that the concentration of nitrogen decreases again.