1.4 Energetics

Question 1

What is enthalpy?

Answer 1

The measure of the heat content (energy) or a substance

Question 2

What is 🔺H

Answer 2

The change in heat content at a constant pressure

Question 3

What is an exothermic reaction?

Answer 3

When heat energy is transferred from the reaction to the surroundings

Question 4

What is an endothermic reaction?

Answer 4

When heat energy is transferred from the surroundings to the reaction

Question 5

What equations do we need to know for calorimetry ?

Answer 5

q=mc🔺T

🔺H=q(inKJ)/moles in reaction

Question 6

What is Hess’ law?

Answer 6

The enthalpy change for a reaction is independent of the route taken

Question 7

What is the equation for working out the enthalpy change of formation? (Type 1)

Answer 7

🔺H= (Sum of 🔺fH products) - (Sum of 🔺fH reactants)

Question 8

What is the enthalpy change of formation

Answer 8

The enthalpy change when one mole of a substance is made from its constituent elements in their standard state under standard conditions

Question 9

What is the equation for working out the enthalpy change of combustion (Type 2)

Answer 9

🔺H= (Sum of 🔺cH reactants) - (Sum of 🔺cH products)

Question 10

What is the enthalpy change of combustion?

Answer 10

The enthalpy change when one mole of a substance is burnt completely in oxygen under standard conditions

Question 11

What is the equation for working out questions involving bond enthalpies?

Answer 11

🔺H= (Sum 🔺H bonds broken) - (Sum of 🔺H bonds made)