⚗️ • Lesson 2.4 : Chemical Energetics, Acids, Bases and Salts (Chem)

Question 1

What is an exothermic reaction?

Answer 1

A reaction that transfers thermal energy to the surroundings, increasing the temperature of the surroundings.

Question 2

What is an endothermic reaction?

Answer 2

A reaction that takes in thermal energy from the surroundings, decreasing the temperature of the surroundings.

Question 3

What do reaction pathway diagrams show?

Answer 3

They show whether a reaction is exothermic or endothermic by comparing the energy of reactants and products.

Question 4

What is the enthalpy change (∆H) of a reaction?

Answer 4

It is the transfer of thermal energy during a reaction.
∆H is negative for exothermic reactions and positive for endothermic reactions.

Question 5

What is activation energy (Ea)?

Answer 5

The minimum energy that colliding particles must have to react.

Question 6

What labels must be included in a reaction pathway diagram?

Answer 6

Reactants, products, overall energy change (∆H), and activation energy (Ea).

Question 7

Is bond breaking endothermic or exothermic?

Answer 7

Endothermic — it requires energy.

Question 8

Is bond making endothermic or exothermic?

Answer 8

Exothermic — It releases energy.

Question 9

What is the difference between a physical change and a chemical change?

Answer 9

A physical change doesn’t alter the chemical composition of a substance,
while a chemical change results in the formation of a new substance.

Question 10

How does changing the concentration of solutions affect the rate of reaction?

Answer 10

Increasing concentration increases the rate of reaction because there are more reactant particles to collide.

Question 11

How does changing the pressure of gases affect the rate of reaction?

Answer 11

Increasing pressure increases the rate of reaction because the gas particles are closer together, leading to more frequent collisions.

Question 12

How does changing the surface area of solids affect the rate of reaction?

Answer 12

Increasing the surface area increases the rate of reaction by providing more area for collisions to occur.

Question 13

How does changing the temperature affect the rate of reaction?

Answer 13

Increasing temperature increases the rate of reaction by giving particles more energy, causing them to collide more often and with more force.

Question 14

How does adding or removing a catalyst affect the rate of reaction?

Answer 14

A catalyst increases the rate of reaction by lowering the activation energy, without being consumed in the reaction.

Question 15

How does collision theory explain the rate of reaction in terms of the number of particles per unit volume?

Answer 15

A higher number of particles per unit volume increases the rate of reaction by increasing the frequency of collisions between reactant particles.

Question 16

What does a catalyst do to the activation energy of a reaction?

Answer 16

A catalyst decreases the activation energy, making it easier for reactions to occur.

Question 17

How can the rate of reaction be practically investigated?

Answer 17

By measuring changes in mass, volume of gas produced, or time taken for the reaction to complete.

Question 18

How does collision theory explain the rate of reaction in terms of the frequency of collisions between particles?

Answer 18

The more frequent the collisions between particles, the higher the rate of reaction, as there are more opportunities for particles to react.

Question 19

How does collision theory explain the rate of reaction in terms of the kinetic energy of particles?

Answer 19

Higher kinetic energy of particles results in more energetic collisions, increasing the likelihood of a successful reaction.

Question 20

How does collision theory explain the rate of reaction in terms of activation energy (Ea)?

Answer 20

A reaction occurs when particles collide with sufficient energy to overcome the activation energy barrier, which is the minimum energy required for the reaction.

Question 21

What are redox reactions?

Answer 21

Redox reactions involve both oxidation (loss of electrons) and reduction (gain of electrons) occurring simultaneously.

Question 22

What is oxidation in terms of the gain of oxygen and loss of electrons?

Answer 22

Oxidation is the process of a substance gaining oxygen during a chemical reaction, and it involves the loss of electrons by a substance.

Question 23

What is oxidation in terms of an increase in oxidation number?

Answer 23

Oxidation occurs when the oxidation number of an element increases during a reaction.

Question 24

What is reduction in terms of gain of electrons?

Answer 24

Reduction is the process where a substance gains electrons during a chemical reaction.

Question 25

What is reduction in terms of a decrease in oxidation number?

Answer 25

Reduction occurs when the oxidation number of an element decreases during a chemical reaction.

Question 26

What are redox reactions in terms of oxygen gain and loss?

Answer 26

Redox reactions involve the gain of oxygen by one substance (oxidation) and the loss of oxygen by another substance (reduction).

Question 27

What are the characteristic properties of acids when reacting with metals?

Answer 27

Acids react with metals to produce *hydrogen gas and a salt.*

Question 28

What are the characteristic properties of acids when reacting with bases?

Answer 28

Acids react with bases to form *a salt and water in a neutralisation reaction.*

Question 29

What are the characteristic properties of acids when reacting with carbonates?

Answer 29

Acids react with carbonates to produce *carbon dioxide gas, water, and a salt.*

Question 30

How do acids affect the indicators litmus and methyl orange?

Answer 30

Acids turn litmus paper red and methyl orange **red.**

Question 31

What are bases, and what are alkalis?

Answer 31

Bases are oxides or hydroxides of metals, and alkalis are soluble bases that dissolve in water.

Question 32

How do bases react with acids?

Answer 32

Bases react with acids to form a salt and water in a neutralisation reaction.

Question 33

How do alkalis affect the indicators litmus and methyl orange?

Answer 33

Alkalis turn litmus paper blue and methyl orange **yellow.**

Question 34

How can you compare neutrality, relative acidity, and relative alkalinity using universal indicator?

Answer 34

Universal indicator shows different colors depending on the **pH**, Red = *acidic (pH 0-6)* Green = *neutral, (pH 7)* Blue/purple = *alkaline (pH 8-14)*

Question 35

What is the *neutralisation* reaction between an acid and an alkali?

Answer 35

The neutralisation reaction between an acid and an alkali produces a salt and water. The ionic equation is not required for this reaction.

Question 36

How can oxides be classified based on their character?

Answer 36

Oxides can be classified as acidic (ex. SO₂ and CO₂) or basic (ex. CuO and CaO) based on whether the oxide is metallic or non-metallic.

Question 37

What are **amphoteric** oxides?

Answer 37

Amphoteric oxides are oxides that can react with both acids and bases to produce a salt and water.

Question 38

Which oxides are amphoteric?

Answer 38

Al₂O₃ and ZnO are examples of amphoteric oxides. (Aluminium Oxide and Zinc Oxide)

Question 39

How is a soluble salt prepared by titration?

Answer 39

Mix an acid with an alkali in exact proportions using a burette and a pH indicator. Evaporate the water to crystallize the salt.

Question 40

How is a soluble salt prepared when reacting an acid with excess metal?

Answer 40

Add excess metal to an acid; the metal reacts to form a salt and hydrogen. Filter out the metal and purify the salt.

Question 41

How is a soluble salt prepared when reacting an acid with excess insoluble base?

Answer 41

Add excess base to an acid; filter out the excess base, then crystallize the salt.

Question 42

How is a soluble salt prepared when reacting an acid with excess insoluble carbonate?

Answer 42

Add excess carbonate to an acid; filter out the excess, then crystallize the salt.

Question 43

What is a hydrated substance?

Answer 43

A hydrated substance is a substance that is chemically combined with water.

Question 44

What is an anhydrous substance?

Answer 44

An anhydrous substance is a substance that contains no water.

Question 45

How are insoluble salts prepared by precipitation?

Answer 45

Mix two solutions containing soluble salts. The insoluble salt forms as a precipitate, which is then filtered, washed, and dried.