Chemistry 11HL
Unit 6 / IB Topic 5.2
Energetics Cycle 2 – Summary Notes Template
Calculating Enthalpy Change (∆H) Experimentally Using Calorimetry
ENERGETICS 2A: Principles of Heat Transfer
What is it? Draw a diagram to represent this principle.
What important assumption is made?
ENERGETICS 2B: Calculating the Heat Change (q) of a Substance
Formula used:
What is the specific heat capacity of water (including units)?
How can a volume be converted to a mass? What assumptions are being made? When are these
assumptions valid?
First problem (slide 16):
A 50.0 cm3 sample of water at 20.0ºC was heated to a temperature of 45.0ºC. Calculate the
heat absorbed by the water.
Second problem (slide 20): (Note that this is more of a Physics problem, but it is a good
way to show how the Principle of Heat Transfer is applied.)
A 10.0 g cylinder of copper at 80.0ºC loses 190 J of heat. Calculate the final temperature of
the copper.
Additional information required: specific heat capacity of copper = 0.39 J g−1 C−1
Chemistry 11HL
Unit 6 / IB Topic 5.2
ENERGETICS 2C: Stoichiometry Returns!
How does a ∆H value relate to a balanced chemical equation?
1.
The molar enthalpy of combustion of ethanol is -1367 kJ mol-1.
C2H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(l) ΔH = -1397 kJ mol-1
a) Calculate the heat released when 0.25 mol of ethanol burn.
b) Calculate the heat released when 2.00 g of ethanol (C2H5OH) burn.
2.
When 4.0 g of sulfur are burned in excess oxygen, 40.0 kJ of heat is evolved.
Calculate the enthalpy change for the combustion of sulfur.
balanced chemical equation:
solution:
3.
The molar enthalpy of combustion of methane is -75 kJ mol-1.
What mass of methane is needed to produce 1.5 x 105 kJ of heat?
balanced chemical equation:
solution:
Chemistry 11HL
Unit 6 / IB Topic 5.2
ENERGETICS 2D: Using Calorimetry Data to Calculate ∆H Values IMPORTANT: What is the difference between a heat value (q) and the enthalpy change (∆H) for a
reaction?
Calculating ∆H Values for Combustion Reactions
Chemistry 11HL
Unit 6 / IB Topic 5.2
Calculating ∆H Values for Reactions in Solutions (aka Aqueous Reactions):
QUESTIONS I HAVE ABOUT USING CALORIMETRY DATA TO FIND ∆H VALUES: