ScienceAges 16-18

Calorimetry & molar enthalpy change

Combine molar mass (n = m ÷ M) and calorimeter heat transfer to determine the magnitude of molar enthalpy of combustion |ΔH|. Review suitability for your learners before teaching.

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Worksheet StudioPractice pack · Ages 16-18

Calorimetry & molar enthalpy change

Take your time. Show your thinking.

1. Complete combustion of 20 g of a fuel (molar mass M = 80 g/mol) releases 135 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 20 g (M = 80 g/mol) · Heat Q = 135 kJ → |ΔH| = Q ÷ n
2. Complete combustion of 200 g of a fuel (molar mass M = 100 g/mol) releases 1520 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 200 g (M = 100 g/mol) · Heat Q = 1520 kJ → |ΔH| = Q ÷ n
3. Complete combustion of 8 g of a fuel (molar mass M = 40 g/mol) releases 128 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 8 g (M = 40 g/mol) · Heat Q = 128 kJ → |ΔH| = Q ÷ n
4. Complete combustion of 120 g of a fuel (molar mass M = 60 g/mol) releases 1000 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 120 g (M = 60 g/mol) · Heat Q = 1000 kJ → |ΔH| = Q ÷ n
5. Complete combustion of 40 g of a fuel (molar mass M = 40 g/mol) releases 460 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 40 g (M = 40 g/mol) · Heat Q = 460 kJ → |ΔH| = Q ÷ n
6. Complete combustion of 24 g of a fuel (molar mass M = 120 g/mol) releases 136 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 24 g (M = 120 g/mol) · Heat Q = 136 kJ → |ΔH| = Q ÷ n
7. Complete combustion of 480 g of a fuel (molar mass M = 120 g/mol) releases 2880 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 480 g (M = 120 g/mol) · Heat Q = 2880 kJ → |ΔH| = Q ÷ n
8. Complete combustion of 240 g of a fuel (molar mass M = 120 g/mol) releases 360 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 240 g (M = 120 g/mol) · Heat Q = 360 kJ → |ΔH| = Q ÷ n
9. Complete combustion of 8 g of a fuel (molar mass M = 40 g/mol) releases 32 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 8 g (M = 40 g/mol) · Heat Q = 32 kJ → |ΔH| = Q ÷ n
10. Complete combustion of 60 g of a fuel (molar mass M = 60 g/mol) releases 440 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 60 g (M = 60 g/mol) · Heat Q = 440 kJ → |ΔH| = Q ÷ n
11. Complete combustion of 20 g of a fuel (molar mass M = 100 g/mol) releases 40 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 20 g (M = 100 g/mol) · Heat Q = 40 kJ → |ΔH| = Q ÷ n
12. Complete combustion of 30 g of a fuel (molar mass M = 60 g/mol) releases 90 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 30 g (M = 60 g/mol) · Heat Q = 90 kJ → |ΔH| = Q ÷ n

12 questions · Seed 46 · Age guidance, not curriculum certification

View the answer key

Worksheet StudioAnswer key · Ages 16-18

Calorimetry & molar enthalpy change

Answers and reasoning. Review before teaching.

1. Complete combustion of 20 g of a fuel (molar mass M = 80 g/mol) releases 135 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
540 kJ/mol
First find moles burned: n = 20 g ÷ 80 g/mol = 0.25 mol. Then |ΔH| = 135 kJ ÷ 0.25 mol = 540 kJ/mol.
2. Complete combustion of 200 g of a fuel (molar mass M = 100 g/mol) releases 1520 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
760 kJ/mol
First find moles burned: n = 200 g ÷ 100 g/mol = 2 mol. Then |ΔH| = 1520 kJ ÷ 2 mol = 760 kJ/mol.
3. Complete combustion of 8 g of a fuel (molar mass M = 40 g/mol) releases 128 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
640 kJ/mol
First find moles burned: n = 8 g ÷ 40 g/mol = 0.2 mol. Then |ΔH| = 128 kJ ÷ 0.2 mol = 640 kJ/mol.
4. Complete combustion of 120 g of a fuel (molar mass M = 60 g/mol) releases 1000 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
500 kJ/mol
First find moles burned: n = 120 g ÷ 60 g/mol = 2 mol. Then |ΔH| = 1000 kJ ÷ 2 mol = 500 kJ/mol.
5. Complete combustion of 40 g of a fuel (molar mass M = 40 g/mol) releases 460 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
460 kJ/mol
First find moles burned: n = 40 g ÷ 40 g/mol = 1 mol. Then |ΔH| = 460 kJ ÷ 1 mol = 460 kJ/mol.
6. Complete combustion of 24 g of a fuel (molar mass M = 120 g/mol) releases 136 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
680 kJ/mol
First find moles burned: n = 24 g ÷ 120 g/mol = 0.2 mol. Then |ΔH| = 136 kJ ÷ 0.2 mol = 680 kJ/mol.
7. Complete combustion of 480 g of a fuel (molar mass M = 120 g/mol) releases 2880 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
720 kJ/mol
First find moles burned: n = 480 g ÷ 120 g/mol = 4 mol. Then |ΔH| = 2880 kJ ÷ 4 mol = 720 kJ/mol.
8. Complete combustion of 240 g of a fuel (molar mass M = 120 g/mol) releases 360 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
180 kJ/mol
First find moles burned: n = 240 g ÷ 120 g/mol = 2 mol. Then |ΔH| = 360 kJ ÷ 2 mol = 180 kJ/mol.
9. Complete combustion of 8 g of a fuel (molar mass M = 40 g/mol) releases 32 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
160 kJ/mol
First find moles burned: n = 8 g ÷ 40 g/mol = 0.2 mol. Then |ΔH| = 32 kJ ÷ 0.2 mol = 160 kJ/mol.
10. Complete combustion of 60 g of a fuel (molar mass M = 60 g/mol) releases 440 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
440 kJ/mol
First find moles burned: n = 60 g ÷ 60 g/mol = 1 mol. Then |ΔH| = 440 kJ ÷ 1 mol = 440 kJ/mol.
11. Complete combustion of 20 g of a fuel (molar mass M = 100 g/mol) releases 40 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
200 kJ/mol
First find moles burned: n = 20 g ÷ 100 g/mol = 0.2 mol. Then |ΔH| = 40 kJ ÷ 0.2 mol = 200 kJ/mol.
12. Complete combustion of 30 g of a fuel (molar mass M = 60 g/mol) releases 90 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
180 kJ/mol
First find moles burned: n = 30 g ÷ 60 g/mol = 0.5 mol. Then |ΔH| = 90 kJ ÷ 0.5 mol = 180 kJ/mol.

12 questions · Seed 46 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 16-18

Calorimetry & molar enthalpy change

Take your time. Show your thinking.

1. Complete combustion of 20 g of a fuel (molar mass M = 80 g/mol) releases 135 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 20 g (M = 80 g/mol) · Heat Q = 135 kJ → |ΔH| = Q ÷ n
2. Complete combustion of 200 g of a fuel (molar mass M = 100 g/mol) releases 1520 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 200 g (M = 100 g/mol) · Heat Q = 1520 kJ → |ΔH| = Q ÷ n
3. Complete combustion of 8 g of a fuel (molar mass M = 40 g/mol) releases 128 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 8 g (M = 40 g/mol) · Heat Q = 128 kJ → |ΔH| = Q ÷ n
4. Complete combustion of 120 g of a fuel (molar mass M = 60 g/mol) releases 1000 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 120 g (M = 60 g/mol) · Heat Q = 1000 kJ → |ΔH| = Q ÷ n
5. Complete combustion of 40 g of a fuel (molar mass M = 40 g/mol) releases 460 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 40 g (M = 40 g/mol) · Heat Q = 460 kJ → |ΔH| = Q ÷ n
6. Complete combustion of 24 g of a fuel (molar mass M = 120 g/mol) releases 136 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 24 g (M = 120 g/mol) · Heat Q = 136 kJ → |ΔH| = Q ÷ n
7. Complete combustion of 480 g of a fuel (molar mass M = 120 g/mol) releases 2880 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 480 g (M = 120 g/mol) · Heat Q = 2880 kJ → |ΔH| = Q ÷ n
8. Complete combustion of 240 g of a fuel (molar mass M = 120 g/mol) releases 360 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 240 g (M = 120 g/mol) · Heat Q = 360 kJ → |ΔH| = Q ÷ n
9. Complete combustion of 8 g of a fuel (molar mass M = 40 g/mol) releases 32 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 8 g (M = 40 g/mol) · Heat Q = 32 kJ → |ΔH| = Q ÷ n
10. Complete combustion of 60 g of a fuel (molar mass M = 60 g/mol) releases 440 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 60 g (M = 60 g/mol) · Heat Q = 440 kJ → |ΔH| = Q ÷ n
11. Complete combustion of 20 g of a fuel (molar mass M = 100 g/mol) releases 40 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 20 g (M = 100 g/mol) · Heat Q = 40 kJ → |ΔH| = Q ÷ n
12. Complete combustion of 30 g of a fuel (molar mass M = 60 g/mol) releases 90 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
Fuel: 30 g (M = 60 g/mol) · Heat Q = 90 kJ → |ΔH| = Q ÷ n

12 questions · Seed 46 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 16-18

Calorimetry & molar enthalpy change

Answers and reasoning. Review before teaching.

1. Complete combustion of 20 g of a fuel (molar mass M = 80 g/mol) releases 135 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
540 kJ/mol
First find moles burned: n = 20 g ÷ 80 g/mol = 0.25 mol. Then |ΔH| = 135 kJ ÷ 0.25 mol = 540 kJ/mol.
2. Complete combustion of 200 g of a fuel (molar mass M = 100 g/mol) releases 1520 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
760 kJ/mol
First find moles burned: n = 200 g ÷ 100 g/mol = 2 mol. Then |ΔH| = 1520 kJ ÷ 2 mol = 760 kJ/mol.
3. Complete combustion of 8 g of a fuel (molar mass M = 40 g/mol) releases 128 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
640 kJ/mol
First find moles burned: n = 8 g ÷ 40 g/mol = 0.2 mol. Then |ΔH| = 128 kJ ÷ 0.2 mol = 640 kJ/mol.
4. Complete combustion of 120 g of a fuel (molar mass M = 60 g/mol) releases 1000 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
500 kJ/mol
First find moles burned: n = 120 g ÷ 60 g/mol = 2 mol. Then |ΔH| = 1000 kJ ÷ 2 mol = 500 kJ/mol.
5. Complete combustion of 40 g of a fuel (molar mass M = 40 g/mol) releases 460 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
460 kJ/mol
First find moles burned: n = 40 g ÷ 40 g/mol = 1 mol. Then |ΔH| = 460 kJ ÷ 1 mol = 460 kJ/mol.
6. Complete combustion of 24 g of a fuel (molar mass M = 120 g/mol) releases 136 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
680 kJ/mol
First find moles burned: n = 24 g ÷ 120 g/mol = 0.2 mol. Then |ΔH| = 136 kJ ÷ 0.2 mol = 680 kJ/mol.
7. Complete combustion of 480 g of a fuel (molar mass M = 120 g/mol) releases 2880 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
720 kJ/mol
First find moles burned: n = 480 g ÷ 120 g/mol = 4 mol. Then |ΔH| = 2880 kJ ÷ 4 mol = 720 kJ/mol.
8. Complete combustion of 240 g of a fuel (molar mass M = 120 g/mol) releases 360 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
180 kJ/mol
First find moles burned: n = 240 g ÷ 120 g/mol = 2 mol. Then |ΔH| = 360 kJ ÷ 2 mol = 180 kJ/mol.
9. Complete combustion of 8 g of a fuel (molar mass M = 40 g/mol) releases 32 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
160 kJ/mol
First find moles burned: n = 8 g ÷ 40 g/mol = 0.2 mol. Then |ΔH| = 32 kJ ÷ 0.2 mol = 160 kJ/mol.
10. Complete combustion of 60 g of a fuel (molar mass M = 60 g/mol) releases 440 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
440 kJ/mol
First find moles burned: n = 60 g ÷ 60 g/mol = 1 mol. Then |ΔH| = 440 kJ ÷ 1 mol = 440 kJ/mol.
11. Complete combustion of 20 g of a fuel (molar mass M = 100 g/mol) releases 40 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
200 kJ/mol
First find moles burned: n = 20 g ÷ 100 g/mol = 0.2 mol. Then |ΔH| = 40 kJ ÷ 0.2 mol = 200 kJ/mol.
12. Complete combustion of 30 g of a fuel (molar mass M = 60 g/mol) releases 90 kJ of thermal energy in a calorimeter. Calculate the magnitude of the molar enthalpy of combustion |ΔH| in kJ/mol.
180 kJ/mol
First find moles burned: n = 30 g ÷ 60 g/mol = 0.5 mol. Then |ΔH| = 90 kJ ÷ 0.5 mol = 180 kJ/mol.

12 questions · Seed 46 · Age guidance, not curriculum certification