(Chapter 4.1) Using Chemistry: Chemical Reactions and Energy

Question 1

What is an exothermic reaction?

Answer 1

An exothermic reaction is a reaction that produces energy

Question 2

What is an endothermic reaction?

Answer 2

An endothermic reaction is a reaction that absorbs energy

Question 3

True or False. Exothermic reactions always release heat (energy).

Answer 3

False. While it is usually heat energy, the energy can be released as electrical, light or some other form.

Question 4

In an exothermic reaction, does the reactants or products have more stored energy?

Answer 4

Reactants

Question 5

In an endothermic reaction, does the reactants or products have more stored energy?

Answer 5

Products

Question 6

Do reactions that break bonds tend to be exothermic or endothermic and why?

Answer 6

It is usually an endothermic reaction as breaking chemical bonds requires a significant amount of energy and endothermic reactions absorb energy.

Question 7

Do reactions that form bonds tend to be exothermic or endothermic and why?

Answer 7

It is usually an exothermic reaction as forming bonds requires no energy. The total energy of bonded atoms is lower than those atoms individually and the excess energy is released.

Question 8

True or False. Every collision between reactants results in a chemical reaction.

Answer 8

False. The particles must collide with enough energy.

Question 9

Define activation energy

Answer 9

The minimum energy necessary for a chemical reaction to occur

Question 10

In what units is activation energy measured in?

Answer 10

Joules(J) or kilojoules (kJ)

Question 11

Is the activation energy higher in A –> B or B –> A given that A –> B is an exothermic reaction and why?

Answer 11

B –> A as endothermic reactions require a higher activation energy as it has a net gain in energy.

Question 12

Using letters as substitution for the anion and cation in the compounds, illustrate a synthesis reaction

Answer 12

A+B –> AB

Question 13

Are synthesis reactions usually exothermic or endothermic?

Answer 13

Exothermic as bonds are formed

Question 14

Are decomposition reactions usually exothermic or endothermic?

Answer 14

Endothermic as bonds are broken

Question 15

What is thermal decomposition?

Answer 15

A decomposition reaction that uses heat to supply energy for the reaction

Question 16

What is the difference between electrolytic decomposition and electrolysis?

Answer 16

There is no difference

Question 17

What is electrolytic decomposition?

Answer 17

A decomposition reaction that uses electricity to supply energy for the reaction

Question 18

Define electrochemical cell

Answer 18

A device that can generate electrical energy from the chemical reactions occurring in it or use the electrical energy supplied to it to facilitate chemical reactions

Question 19

What is the name of the electrochemical cell produces energy?

Answer 19

Voltaic or galvanic cell

Question 20

What is the name of the electrochemical cell that uses energy?

Answer 20

Electrolytic cell

Question 21

Name the components of an electrochemical cell

Answer 21

Electrode, liquid electrolyte, dissolved ionic substance, and a porous membrane

Question 22

What is the ‘informal’ term for a porous membrane?

Answer 22

A ‘salt-bridge’

Question 23

Define electrolyte

Answer 23

A medium that contains ions that can conduct electricity

Question 24

Define electrode

Answer 24

An electrical conductor that makes contact with the nonmetallic circuit parts of a circuit. (It is also a pokemon lol)

Question 25

Define half-cell

Answer 25

1 of the 2 an electrochemical cell containing an electrode and an electrolyte

Question 26

Define anode

Answer 26

An electrode with a negative charge

Question 27

Define cathode

Answer 27

An electrode with a positive charge

Question 28

What is the role of the electrodes in an electrochemical cell?

Answer 28

The role of electrodes is to transfer/move the cations (positive ions). This occurs through the release or absorption of cations by the electrodes in order to become stable

Question 29

What is the role of the liquid electrolyte in an electrochemical cell?

Answer 29

The role of the liquid electrolyte is to provide a medium that enables movement of the cations

Question 30

What is the role of the dissolved ionic substance?

Answer 30

The role of the dissolved ionic substance is to facilitate the release and absorption of cations

Question 31

What is the role of the porous membrane?

Answer 31

The role of the porous membrane is to enable the movement of the cation between the 2 half-cells

Question 32

What causes an electric current in an electrochemical cell?

Answer 32

The movement of cations results in the movement of electrons in the opposite direction

Question 33

When does electricity stop flowing in an electrochemical cell?

Answer 33

It stops flowing when a half-cell runs out of substances necessary for its reaction

Question 34

Define by-product

Answer 34

A substance produced as a direct result of the desired reaction

Question 35

Is sponge cake a suitable electrochemical cell and why?

Answer 35

Not suitable. Electrochemical cells require an electrode and electrolyte and as sponge cake has no juice/liquid electrolyte