Endothermic And Exothermic

Question 1

What is an exothermic reaction?

Answer 1

An exothermic reaction is one which gives out energy to the surroundings, usually in the form of heat.

Combustion reactions are a common example of exothermic reactions.

Question 2

What is an endothermic reaction?

Answer 2

An endothermic reaction is one which takes in energy from the surroundings, usually in the form of heat.

This is typically shown by a fall in temperature of the surroundings.

Question 3

What is the significance of reaction profiles?

Answer 3

Reaction profiles show the energy levels of the reactants and the products in a reaction, helping to determine if energy is released or taken in.

They illustrate whether a reaction is exothermic or endothermic.

Question 4

In an exothermic reaction, where are the energy levels of the products compared to the reactants?

Answer 4

The products are at a lower energy than the reactants.

The difference in height represents the energy given out in the reaction.

Question 5

In an endothermic reaction, where are the energy levels of the products compared to the reactants?

Answer 5

The products are at a higher energy than the reactants.

The difference in height represents the energy taken in during the reaction.

Question 6

Fill in the blank: An exothermic reaction is one that _______ energy.

Answer 6

gives out

Question 7

Fill in the blank: An endothermic reaction _______ energy from the surroundings.

Answer 7

takes in

Question 8

True or False: Combustion reactions are always endothermic.

Answer 8

False

Question 9

What does the difference in height in a reaction profile represent for an exothermic reaction?

Answer 9

The energy given out in the reaction.

Question 10

What does the difference in height in a reaction profile represent for an endothermic reaction?

Answer 10

The energy taken in during the reaction.

Question 11

What is the chemical equation for the combustion of methane in air?

Answer 11

CH₄ + 2O₂ → CO₂ + 2H₂O

Question 13

What is an endothermic reaction?

Answer 13

A reaction that absorbs energy from its surroundings

Endothermic reactions typically lead to a decrease in temperature of the surroundings.

Question 14

What is an exothermic reaction?

Answer 14

A reaction that releases energy to its surroundings

Exothermic reactions usually result in an increase in temperature of the surroundings.

Question 15

What is activation energy?

Answer 15

The minimum amount of energy needed for bonds to break and a reaction to start

Activation energy can be visualized as the energy needed to climb a hill before descending.

Question 16

How is activation energy represented on a reaction profile?

Answer 16

As the energy difference between the reactants and the highest point on the curve

Question 17

What happens if the energy input is less than the activation energy?

Answer 17

Nothing will happen; the reaction will not start.

Question 18

What is the purpose of using a polystyrene cup in temperature measurement during reactions?

Answer 18

To provide insulation and limit energy transfer to or from the reaction mixture

Question 19

What is the first step in measuring temperature changes during a reaction?

Answer 19

Put a polystyrene cup into a large beaker of cotton wool

Question 20

What should you do after adding the first reagent to the polystyrene cup?

Answer 20

Measure the initial temperature of the solution

Question 21

What is the importance of putting a lid on the polystyrene cup during the reaction?

Answer 21

To reduce energy lost by evaporation

Question 22

What do you calculate after recording the maximum or minimum temperature during a reaction?

Answer 22

The temperature change

Question 23

Fill in the blank: The energy needed to get a reaction going is called _______.

Answer 23

[activation energy]

Question 24

What variables can affect the amount of energy transferred in a reaction?

Answer 24

The mass or concentration of the reactants

Question 25

True or False: Insulation is not important in measuring temperature changes in reactions.

Answer 25

False

Question 26

What should be done to ensure accurate temperature change readings?

Answer 26

Insulate the reaction mixture properly

Question 27

What is the role of cotton wool in the experimental setup?

Answer 27

To provide insulation to the polystyrene cup

Question 28

What is the outcome when you stir the reaction mixture after adding the second reagent?

Answer 28

It helps to initiate and mix the reaction.

Question 29

What type of reaction is characterized by a temperature decrease when ammonium chloride is dissolved in water?

Answer 29

Endothermic reaction ## Footnote Dissolving ammonium chloride decreases the temperature of the reaction mixture.

Question 30

What happens to the temperature when calcium chloride is dissolved in water?

Answer 30

Temperature rises ## Footnote Dissolving calcium chloride causes the temperature of the solution to rise, indicating an exothermic reaction.

Question 31

What is formed in a neutralisation reaction?

Answer 31

Salt and water ## Footnote In a neutralisation reaction, an acid and a base react to form a salt and water.

Question 32

Are most neutralisation reactions endothermic or exothermic?

Answer 32

Exothermic ## Footnote Most neutralisation reactions, such as HCl + NaOH, are exothermic.

Question 33

What type of neutralisation reaction occurs between ethanoic acid and sodium carbonate?

Answer 33

Endothermic ## Footnote The neutralisation reaction between ethanoic acid and sodium carbonate is endothermic.

Question 34

What is a characteristic of a displacement reaction?

Answer 34

More reactive element displaces a less reactive element ## Footnote In a displacement reaction, a more reactive element displaces a less reactive element in a compound.

Question 35

What type of reaction is typically exothermic and involves the release of energy?

Answer 35

Displacement reaction ## Footnote Displacement reactions are accompanied by a release of energy, making them exothermic.

Question 36

What do precipitation reactions produce?

Answer 36

Insoluble solids ## Footnote Precipitates are insoluble solids formed when two solutions are mixed together.

Question 37

Are precipitation reactions typically endothermic or exothermic?

Answer 37

Exothermic ## Footnote Precipitation reactions are exothermic, as seen in the reaction between lead(II) nitrate and potassium iodide forming a lead iodide precipitate.

Question 38

Fill in the blank: Dissolving _______ decreases the temperature of the reaction mixture.

Answer 38

ammonium chloride ## Footnote This indicates that the reaction is endothermic.

Question 39

Fill in the blank: In a neutralisation reaction, an acid and a base react to form a _______ and water.

Answer 39

salt ## Footnote This is a fundamental concept in chemistry regarding neutralisation.