9.4 Hess' law and enthalpy cycles

Question 1

Hess’s law:
don’t need to memorise

Answer 1

states that, if a reaction can take place by two routes, and the starting and finishing conditions are the same, the total enthalpy change is the same for each route

Question 2

enthalpy changes from ΔfH ⦵
Fe2O3(s) + 3Ca(s) –> 2Fe(s) + 3CaO(s)

Answer 2

a b
▽ =
c
[A] Fe2O3(s) + 3Ca(s) ———–> [B] 2Fe(s) + 3CaO(s)
[C] elements (Fe(s), Ca(s), O2(g))

products - reactants

Question 3

enthalpy changes from ΔfH ⦵

Answer 3

products - reactants

Question 4

enthalpy changes from ΔcH ⦵
4C(s) + 5H2O(g) –> C4H10(g)

Answer 4

a b
▽ =
c
[A] 4C(s) + 5H2O(g) ————> [B] C4H10(g)
[C] combustion products (CO2(g), H2O(l))

reactants - products

Question 5

enthalpy changes from ΔcH ⦵

Answer 5

reactants - products