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Calorimetry - Coggle Diagram
Calorimetry
What is it?
Measuring enthalpy
changes experimentally
Definition
Transferring heat to known mass
of another substance (usually H2O)
and measuring temp rise
Enthalpy of Combustion Reactions
(of an alcohol)
apparatus
copper can used as calorimeter
copper good conductor of heat
low specific heat capacity
does not absorb too much heat
source of
errors
temperature measurement
(use sensors)
heat loss to air
(side shields)
copper absorbing
some heat
(thinner can)
following measurements
taken:
mass of water (g)
temperature rise
of water (K)
loss in mass of fuel (g)
(mass of fuel burned)
method
weigh known mass water
in metal can + note temp
weigh spirit burner
containing ethanol
place under metal can +
light the wick
stir water + note final
temp of water
extinguish spirit burner
and reweigh
diagram
Enthalpy of Neutralisation
of an Acid + Base
method
50cm3 of 2.0 moldm-3 solution
HCl in insulated polystyrene cup
note its temperature
Add 60cm3 of 2.0 moldm-3
NaOH solution (excess to ensure
complete reaction of acid)
Stir continuously with
thermometer & note
MAXIMUM temperature
apparatus
Polystyrene cups used as calorimeters
excellent insulators
low specific heat capacity.
source of
errors
heat loss to surroundings
put lid on polystyrene cup
place polystyrene in beaker
diagram
Enthalpy Changes of
Solution
when ionic solids dissolve
in water, ions in lattice become spread through solution
water good solvent for ionic
water molecules polar
strongly attracted to charged ions
less polar solvents poorer at
dissolving ionic solids
energy released solvation of ions
not compensate
for energy put in
to break up lattice
energy must be
put in
to PULL LATTICE APART
energy is
released
as ATTRACTIONS FORM between ions + water molecules
(hydration) (+ w/ other solvents = solvation)
diagram
Hydration energy
D: energy released when 1 mole of
ions become attached to water molecules
in solution (exothermic)
Lattice energy
D: energy required to break 1 mole
of ionic lattice into constituent ions
(endothermic)
Heat of solution
D: sum of lattice + hydration energies
ΔHsoln = ΔHlattice + ΔHhydration
Enthalpy change of Solution
D: enthalpy change that occurs when 1 mole
of solute dissolved in water to form an
infinitely dilute solution