Calorimetric
Equations II and
Delicious
Applications
Putting it Together
Calorimetry
What is Calorimetry?
What is a Calorimeter?
Three Assumptions of Simple
Calorimeters:
1. No heat is transferred between the
calorimeter and the outside environment
2. Any heat absorbed or released by the
calorimeter materials, such as the container,
is negligible
3. A dilute aqueous solution is assumed to
have a density and specific heat capacity
equal to that of pure water (1.00g/ml and
4.184 J/g°C)
 Solution
 Combustion
 Neutralization
 (Vaporization)
Remember what we’ve seen
 ΔH = nΔHx
 ΔHsystem = ±|qsurroundings|
 q = mcΔT
 n = m/MM
n=CxV
Doing Calorimetric problems
is about using these
equations
ΔH = nΔHx
ΔHsystem = ±|qsurroundings|
nΔHx = qsurroundings
nΔHx = mcΔT
n = mcΔT / ΔHx
m/MM = mcΔT / ΔHx
Calorimetry of Solution
 One substance dissolves in another
NaBr(s)  Na+(aq) + Br-(aq)
Heat of Solution Demo
 http://www.teachersdomain.org/resource/lsps07.sci.phy
s.matter.dissolvesalt/
Calorimetry of Combustion
 Burn a substance in oxygen to yield
CO2 and H2O
C3H8(l) + 5O2(g)  3CO2(g) + 4H2O(l)
Question 3
 If the molar enthalpy of combustion
of propane is -2220KJ/mol, what
mass of propane will have to be
burned in order to raise the
temperature of 1.00L of water from
50.0 to 85°C.
Question 4
 A calorimeter (C=0.850J/˚C)
containing 5.00 x 102 ml of water at
22 oC is warmed to 100oC when
9.00 g of cheddar cheese is burned.
Calculate the heat absorbed by the
water and the heat of combustion,
per gram, of cheese.
Calorimetry of Neutralization
 Acid + Base  Salt + Water
 HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
 Use the same strategy for other reactions
 CuSO4(aq) + 2NaOH(aq) → Cu(OH)2(s) + Na2SO4(aq)
Neutralization demo
 50ml of 1 mol/L HCl
 50ml of 1 mol/L NaOH
(strong acid)
(strong base)
 HCl + NaOH  NaCl + H2O
Question 5
 A chemist wanted to find the heat of neutralization of
HCl with NaOH. She added 61.1ml of 0.543M HCl to
42.6ml of 0.779M NaOH. The initial temperature of both
solutions was 17.8oC and the highest recorded
temperature of the solution after neutralization was
21.6˚C. What is the enthalpy of neutralization of HCl?
 ASSUME: The density and heat capacity of the
solutions is the same as that for pure water
Question 6
 50.0 mL of 0.300 mol/L CuSO4 solution is mixed with
an equal volume of 0.600 mol/L NaOH. The initial
temperature of both solutions is 21.4oC. After mixing
the solutions in the coffee-cup calorimeter, the highest
temperature that is reached is 24.6oC. Determine the
enthalpy change of the reaction.
 CuSO4(aq) + 2NaOH(aq) → Cu(OH)2(s) +
Na2SO4(aq)
But wait, there’s more…
 Heat of Vaporization
H2O(l) + ∆H  H2O(g)
How a fridge works
Heats of Vaporization
 Freon – qvap 232kj/kg
 Water – qvap 2257 kj/kg
 Propane – qvap428 kj/kg
 Ammonia – qvap 1369 kj/kg
 Ethyl Alcohol – qvap 846 kj/kg
So Why Use Freon
 Unreactive
 Chemically Safe
 High qvap
 Boiling point below target temp
 WHY NOT?
 Chlorofluorocarbon
 BAD FOR THE ENVIRONMENT!!!!
Making Ice Cream
Who knew thermochemistry could taste so good?
Ingredients
 (½ cup)
125ml Milk (we’re using 2%)
 (½ cup)
125ml Cream (we’re using 35%)
 (¼ cup)
67.5g Sugar
 (¼ tsp)
~1ml Vanilla Extract/flavouring
For the bag:
 (½ to 1 cup)
250g Sodium Chloride
 (2 cups)
500g ice
Heat of Solution
 Why are we adding salt?
 What does salt do to the melting point/freezing point of
ice/water?
 Why not just use ice?
 Why not use a more endothermic substance i.e.
NH3NO3?
 Why do we salt our roads?
Recipe…I mean…Procedure
 Add ingredients to small bag
 CLOSE IT TIGHTLY (push out most of the air)
 Put the small bag in the big bag
 Add ice and salt to the big bag
 CLOSE IT TIGHTLY
 Swish the big bag back and forth
 Caution: it will get really cold (duh…but seriously, its colder
than you’d think)
Mr. Sheps Ice Cream Attempts
 Which one has sugar? Which one has a higher fat
content?
Let’s Make Ice Cream