VCE Unit 3- Thermochemistry notes + Practice
SAC (with solutions)
(based on VCAA Study Design key knowledge points)
Reference: Victorian Curriculum and Assessment Authority. (2022). VCE Chemistry Study Design.
https://www.vcaa.vic.edu.au/sites/default/files/2026-02/2023ChemistrySD.docx
Contents
1. Stoichiometry in combustion reactions (at SLC).............................................................2
2. Using specific heat capacity of water (fuel & food calorimetry).....................................3
3. Solution calorimetry....................................................................................................... 4
4. Energy from fuels and food............................................................................................. 6
a) Energy transformation efficiency................................................................................. 6
b) Energy values of foods................................................................................................ 6
Practice SAC- Thermochemistry.......................................................................................... 7
Data................................................................................................................................. 7
Question 1 – Combustion stoichiometry (8 marks)..........................................................7
Question 2 – Gas volume calculations & greenhouse gases (7 marks)............................8
Question 3 – Heat energy using specific heat capacity (8 marks)...................................8
Question 4 – Solution calorimetry (8 marks)...................................................................8
Question 5 – Energy transformation efficiency (7 marks)................................................8
Question 6 – Energy from food (6 marks)........................................................................9
Question 7 – Extended response (6 marks).....................................................................9
Marking Guide & Sample Answers...................................................................................... 9
, 1. Stoichiometry in combustion reactions (at SLC)
calculations related to the application of stoichiometry to reactions involving the combustion of fuels,
including mass-mass, mass-volume and volume-volume stoichiometry, to determine heat energy
released, reactant and product amounts and net volume or mass of major greenhouse gases
(CO2, CH4 and H2O), limited to standard laboratory conditions (SLC) at 25 °C and 100 kPa (VCAA,
2022, p. 39)
Key ideas
Combustion = reaction with oxygen producing energy (exothermic)
Fuels are typically hydrocarbons or alcohols
Products of complete combustion:
o CO₂(g)
o H₂O(g) (or sometimes H₂O(l), depending on context)
Calculations are limited to SLC:
o 25 °C
o 100 kPa
o Molar volume of a gas at SLC = 24.8 L mol⁻¹
Balanced chemical equations
Students must be able to:
o Write and balance combustion equations
o Identify mole ratios for calculations
Example:
Stoichiometric calculations to include
Mass–mass
Convert mass → moles → use mole ratio → moles → mass
Example uses:
Mass of fuel burned → mass of CO₂ produced
Mass of fuel → mass of water produced
Worked example:
Propane is used as a fuel. Calculate the mass of CO₂ produced when 11.0 g of propane undergoes complete combustion.
Step 1: Write a balanced equation
C3 H 8 (g)+5 O 2 ( g)→ 3 CO2 ( g)+4 H 2 O( g)
Step 2: Convert mass of propane to moles
11.0
n(C3 H8 )= =0.250 mol
44.0
Step 3: Use mole ratio
1 mol C 3 H8 → 3 mol CO2n( CO2)=0.250 ×3=0.750 mol
Step 4: Convert moles to mass
m(CO 2)=0.750 × 44.0=33.0 g
Answer: 33.0 g of CO₂ is produced.
Mass–volume (gas)
Use when one substance is a gas
Convert mass → moles → volume using:
SAC (with solutions)
(based on VCAA Study Design key knowledge points)
Reference: Victorian Curriculum and Assessment Authority. (2022). VCE Chemistry Study Design.
https://www.vcaa.vic.edu.au/sites/default/files/2026-02/2023ChemistrySD.docx
Contents
1. Stoichiometry in combustion reactions (at SLC).............................................................2
2. Using specific heat capacity of water (fuel & food calorimetry).....................................3
3. Solution calorimetry....................................................................................................... 4
4. Energy from fuels and food............................................................................................. 6
a) Energy transformation efficiency................................................................................. 6
b) Energy values of foods................................................................................................ 6
Practice SAC- Thermochemistry.......................................................................................... 7
Data................................................................................................................................. 7
Question 1 – Combustion stoichiometry (8 marks)..........................................................7
Question 2 – Gas volume calculations & greenhouse gases (7 marks)............................8
Question 3 – Heat energy using specific heat capacity (8 marks)...................................8
Question 4 – Solution calorimetry (8 marks)...................................................................8
Question 5 – Energy transformation efficiency (7 marks)................................................8
Question 6 – Energy from food (6 marks)........................................................................9
Question 7 – Extended response (6 marks).....................................................................9
Marking Guide & Sample Answers...................................................................................... 9
, 1. Stoichiometry in combustion reactions (at SLC)
calculations related to the application of stoichiometry to reactions involving the combustion of fuels,
including mass-mass, mass-volume and volume-volume stoichiometry, to determine heat energy
released, reactant and product amounts and net volume or mass of major greenhouse gases
(CO2, CH4 and H2O), limited to standard laboratory conditions (SLC) at 25 °C and 100 kPa (VCAA,
2022, p. 39)
Key ideas
Combustion = reaction with oxygen producing energy (exothermic)
Fuels are typically hydrocarbons or alcohols
Products of complete combustion:
o CO₂(g)
o H₂O(g) (or sometimes H₂O(l), depending on context)
Calculations are limited to SLC:
o 25 °C
o 100 kPa
o Molar volume of a gas at SLC = 24.8 L mol⁻¹
Balanced chemical equations
Students must be able to:
o Write and balance combustion equations
o Identify mole ratios for calculations
Example:
Stoichiometric calculations to include
Mass–mass
Convert mass → moles → use mole ratio → moles → mass
Example uses:
Mass of fuel burned → mass of CO₂ produced
Mass of fuel → mass of water produced
Worked example:
Propane is used as a fuel. Calculate the mass of CO₂ produced when 11.0 g of propane undergoes complete combustion.
Step 1: Write a balanced equation
C3 H 8 (g)+5 O 2 ( g)→ 3 CO2 ( g)+4 H 2 O( g)
Step 2: Convert mass of propane to moles
11.0
n(C3 H8 )= =0.250 mol
44.0
Step 3: Use mole ratio
1 mol C 3 H8 → 3 mol CO2n( CO2)=0.250 ×3=0.750 mol
Step 4: Convert moles to mass
m(CO 2)=0.750 × 44.0=33.0 g
Answer: 33.0 g of CO₂ is produced.
Mass–volume (gas)
Use when one substance is a gas
Convert mass → moles → volume using:
