Module 4

Question 1

Define exothermic reaction

Answer 1

Exothermic Reaction releases energy, particularly in the form of heat – usually results from the formation of chemical bonds; tends to be synthesis

Question 2

Define endothermic reaction

Answer 2

Endothermic Reaction absorbs energy, particularly in the form of heat – usually results from the breakage of chemical bonds; tends to be decomposition

Question 3

True or False. If ΔH is positive, the reaction is exothermic and if ΔH is negative, the reaction is endothermic

Answer 3

False.

Question 4

Identify how calorimetry can be improved

Answer 4

Improving the calorimetry:
- Putting a lid on the container
- Insulating the beaker of water
- Proximity of flame to beaker

Question 5

Identify the types of catalysts

Answer 5

Types of Catalysts:
- Homogenous catalyst
Heterogenous catalyst

Question 6

Define homogenous catalyst

Answer 6

Homogeneous Catalysts are in the same physical state as the reactants and products of the reaction

Question 7

Define heterogeneous catalyst

Answer 7

Heterogeneous Catalysts are in a different physical state from the reactants and products of the reaction – e.g. surface catalyst

Question 8

Identify the types of latent heat

Answer 8

Types of Latent Heat:
- Latent Heat of Vapourisation
- Latent Heat of Fusion

Question 9

Define bond energy

Answer 9

Bond Energy is the energy necessary to break 1 mole of chemical bonds into its constituent gaseous atoms under standard conditions

Question 10

Define Hess’s Law

Answer 10

Hess’s Law states that the amount of heat energy released or absorbed in a chemical reaction is constant, regardless of the order and number of steps, provided that the same reactants and products are involved

Question 11

Identify the chemical equation for photosynthesis

Answer 11

Carbon Dioxide + Water → Glucose + Oxygen

Question 12

Identify the chemical equation for cellular respiration

Answer 12

Glucose + Oxygen → Carbon Dioxide + Water

Question 13

State the First Law of Thermodynamics

Answer 13

The First Law of Thermodynamics states energy cannot be created nor destroyed – law of conservation of energy

Question 14

State the Second Law of Thermodynamics

Answer 14

The Second Law of Thermodynamics states, over time, the entropy of the universe is increasing; expressed mathematically as: ΔSsystem + ΔSsurroundings = ΔSuniverse > 0

Question 15

State the Third Law of Thermodynamics

Answer 15

The Third Law of Thermodynamics states that the entropy of a perfect crystal is zero at absolute zero

Question 16

Define entropy

Answer 16

Entropy (ΔS) is a measure of the disorder in a system

Question 17

Define spontaneity

Answer 17

Spontaneity is if a reaction can occur without any additional energy input

Question 18

True or False. Gibbs free energy (ΔG) determines the spontaneity of a chemical reaction

Answer 18

True.
Where:
ΔG < -10, the reaction is spontaneous
ΔG > 10, the reaction is non-spontaneous
-10 < ΔG < 10, the reaction is in equilibrium

Question 19

Define Standard Enthalpy of Formation

Answer 19

Standard Enthalpy of Formation (ΔH0f) is the change in enthalpy when 1 mole of a compound is formed in its standard state from its elements in their standard state

Question 20

Identify the limitations of using bond energy to estimate enthalpy change

Answer 20

• Not accurate – exception diatomic molecules are accurate – as they are averages – especially noticeable in larger molecules
• Does not consider environment - pressure or temperature
• Assumes substances are in the gaseous state

Question 21

Explain why bond energy is always negative

Answer 21

Bond Energy is the energy of the formation of bonds, which releases energy hence to measure enthalpy, it has to be negative

Question 22

Define enthalpy

Answer 22

The total energy possessed by a substance