Reaction Types and
Enthalpy Changes
Common Reaction Types:
Formation Reaction – reactants are 2
or more elements that react together
to produce a compound
Molar enthalpy of formation (fH)
values found in data booklet (pg. 4-5)
Formation of dinitrogen tetroxide
Simple Decomposition Reaction –
reactant is a compound that is broken
down into its various elements
Decomposition is the opposite of
formation
Molar enthalpy of simple decomposition
(sdH) will be the opposite sign of the
molar enthalpy of formation (fH) values
found in data booklet (pg. 4-5)
Decomposition of magnesium carbonate
Combustion Reaction – a hydrocarbon
fuel reacts with oxygen to produce
carbon dioxide and water (in most
cases)
Products are gases
Each fuel has a unique molar enthalpy
of combustion (cH)
Combustion of ethane
cH for ethane is -1560 kJ/mol
Single Replacement Reaction – an
element and a dissolved ionic
compound react to produce a different
element and ionic compound (partner
swap between metal element and
metal ion) (in most cases)
Reaction between aluminium and
hydrochloric acid
rH for aluminium is -256 kJ/mol
Double Replacement Reaction – two
dissolved ionic compounds react to
produce a precipitate OR an acid and a
base react in a neutralization reaction
Calcium nitrate reacts with
ammonium phosphate
rH for calcium nitrate is -36 kJ/mol
Calculating
Amounts
Two most common methods to
calculate amounts:
𝑚
𝑛=
𝑀
𝑛=𝑐𝑉
What amount of potassium phosphate
has a mass of 225 g?
What amount of sodium hydroxide is
dissolved in 220 mL of 1.30 x 102 M
solution?
(M is shorthand for mol/L)