Rates 2

Question 1

What is the magnesium and hydrochloric acid experiment used to investigate?

Answer 1

The effect of acid concentration on the rate of reaction.

Question 2

What is measured in the magnesium and acid experiment?

Answer 2

The volume of hydrogen gas produced over time.

Question 3

What type of graph is produced from this experiment?

Answer 3

Volume of gas (y-axis) against time (x-axis).

Question 4

What is the sodium thiosulfate and hydrochloric acid experiment used for?

Answer 4

To observe how temperature affects the rate of reaction.

Question 5

What is observed in the thiosulfate experiment?

Answer 5

A cross under the flask disappears due to a cloudy precipitate.

Question 6

What causes the cloudiness in the thiosulfate experiment?

Answer 6

Formation of sulfur as a solid product.

Question 7

What is the rate of reaction formula?

Answer 7

Rate = change in quantity ÷ time.

Question 8

How do you calculate the rate from a graph?

Answer 8

Find the gradient (change in y ÷ change in x).

Question 9

What does a steeper line on a rate graph show?

Answer 9

A faster reaction.

Question 10

What does a horizontal line on a rate graph show?

Answer 10

The reaction has finished—no more products being formed.

Question 11

What is the gradient of a tangent used for?

Answer 11

To find the instantaneous rate at a specific time.

Question 12

What is a reversible reaction?

Answer 12

A reaction where products can react to form the original reactants again.

Question 13

What symbol shows a reversible reaction?

Answer 13

A double arrow: ⇌

Question 14

Give an example of a reversible reaction.

Answer 14

Hydrated copper sulfate ⇌ anhydrous copper sulfate + water.

Question 15

What happens in the forward reaction of copper sulfate?

Answer 15

Hydrated copper sulfate loses water to become white anhydrous copper sulfate.

Question 16

What is dynamic equilibrium?

Answer 16

The point where the forward and reverse reactions occur at the same rate.

Question 17

Does concentration change at equilibrium?

Answer 17

No, concentrations remain constant (though reactions continue).

Question 18

What conditions are required for equilibrium?

Answer 18

A closed system where no substances enter or leave.

Question 19

What is Le Chatelier’s Principle?

Answer 19

If conditions change, the system shifts to oppose the change and restore equilibrium.

Question 20

What happens if concentration of a reactant increases?

Answer 20

The system shifts to use it up by favouring the forward reaction.

Question 21

What happens if temperature is increased in an exothermic reaction?

Answer 21

The system favours the endothermic (reverse) reaction.

Question 22

What happens if pressure is increased in a gas reaction?

Answer 22

Equilibrium shifts to the side with fewer gas molecules.

Question 23

What is an example of a reversible industrial reaction?

Answer 23

The Haber Process: N₂ + 3H₂ ⇌ 2NH₃.

Question 24

What conditions favour ammonia formation in the Haber Process?

Answer 24

High pressure and low temperature (but a compromise is used).

Question 25

Why is a catalyst used in reversible reactions?

Answer 25

To speed up both forward and reverse reactions without affecting position of equilibrium.