Energetics

Question 1

What is the definition for enthalpy change

Answer 1

Enthalpy change is the amount of heat energy taken in or given out during any change in a system provided the pressure is constant

Question 2

What is the enthalpy change in an exothermic reaction

Answer 2

Exothermic means energy is transferred from the system to the surroundings. This means the products have less enthalpy than the reactants

Question 3

What is the enthalpy change in an exothermic reaction

Answer 3

Exothermic means energy is transferred from the system to the surroundings. This means the products have less enthalpy than the reactants

Question 4

What is the enthalpy change for an endothermic reaction

Answer 4

In and endothermic change heat energy is transferred from the surroundings to the system. This requires an input of heat energy, meaning the products have more enthalpy than the reactants

Question 5

Equation for enthalpy change ΔH

Answer 5

ΔH = H(products) - H(reactants)

Question 6

ΔH in exothermic reactions

Answer 6

ΔH is negative

Question 7

ΔH in an endothermic reaction

Answer 7

ΔH is positive

Question 8

Examples of oxidation exothermic processes

Answer 8

Combustion of fuels, the oxidation of carbohydrates (glucose in respiration)

Question 9

What is the standard enthalpy change of formation

Answer 9

The enthalpy change when 1 mole of a compound is formed from its elements under standard condition (298K and 100kpa), all reactants and products being in their standard states

Question 10

What is the standard enthalpy change of combustion

Answer 10

the enthalpy change that occurs when one mole of a substance is combusted completely in oxygen under standard conditions (298K and 100kPa), all reactants and products being in their standard states

Question 11

What is the enthalpy change of reaction

Answer 11

The enthalpy change when the number of moles of reactants as specified in the balanced equation react together