[9.1] enthalpy changes

Question 1

what is involved in the reactant?

Answer 1

• breaking bonds
• need energy
• endothermic

Question 2

what is involved in the product?

Answer 2

• making bonds
• releases energy
• exothermic

Question 3

what are examples of exothermic reactions?

Answer 3

• combustion of fuels
• respiration
• neutralisation

Question 4

what are examples of endothermic reactions?

Answer 4

• photosynthesis
• thermal decomposition of calcium carbonate

Question 5

what is the definition of standard enthalpy change of reaction? (ΔᵣH°)

Answer 5

it is the enthalpy change of a reaction in the molar quantities stated measured at standard conditions with all substances in their naturally occurring states

Question 6

what is the standard enthalpy changes of formation? (ΔfH°)

Answer 6

the enthalpy change when 1 mole of a substance is formed from its constituent elements with all reactants and products in standard states under standard conditions (products must have 1 mole)

Question 7

what is the standard enthalpy change of combustion? (ΔcH°)

Answer 7

the enthalpy change when 1 mole of a substance is completely burned in oxygen with all reactants and products in standard states under standard conditions (reactants must have 1 mole)

Question 8

what is the standard enthalpy change of neutralisation? (ΔₙₑᵤₜH°)

Answer 8

the enthalpy change when 1 mole of water is formed in a reaction between an acid and alkali under standard conditions (water must have 1 mole)

Question 9

what is a standard state?

Answer 9

• the physical state of a substance under standard conditions
• standard conditions are 100 kPa and 298 K