1.4 energetics

Question 0

c: What sign is given to an exothermic reaction?

Answer 0

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Question 1

a: Define enthalpy change.

Answer 1

the [change in thermal energy] when a reaction is carried out at [constant pressure]

Question 3

d: Define enthalpy of formation.

Answer 3

the [energy change] when one mole of a [compound in its standard state] is formed from its [elements in their standard states] [298K 1atm]

Question 3

d: Define enthalpy of atomisation.

Answer 3

the [energy change] when [one mole] of [gaseous atoms] is formed from the [element under standard conditions]

Question 4

d: Define enthalpy of combustion.

Answer 4

the [energy change] when [one mole of a compound] burns [completely in oxygen] [298K 1atm]

Question 5

d: Define enthalpy of neutralisation.

Answer 5

the [energy change] when [one mole of water] is formed in a neutralisation reaction

Question 6

e: State Hess’s Law.

Answer 6

the enthalpy change between reactants and products is the same regardless of the route taken

Question 7

f: How do you calculate ΔΗ of a reaction when heating water is involved?

Answer 7

ΔΗ (J) = mass (of H2O) * heat capacity (4.2 for H2O) * ΔΤ (C)

Question 8

g: Define mean bond enthalpy.

Answer 8

the energy required to [break one mole of the bonds] in the [gaseous state], [averaged] over various compounds