Calculate the molar mass of propane, C3H8. Select one: 44.1 g/mol 36.0 g/mol 24.0 g/mol 60.1 g/mol 26.0 g/mol
The correct answer and explanation is:
Correct Answer: 44.1 g/mol
To calculate the molar mass of propane (C₃H₈), we add together the atomic masses of all the atoms in one molecule of propane.
Propane consists of:
- 3 carbon atoms (C)
- 8 hydrogen atoms (H)
From the periodic table:
- The atomic mass of carbon (C) ≈ 12.01 g/mol
- The atomic mass of hydrogen (H) ≈ 1.008 g/mol
Now, calculate the total mass of each element in propane:
Carbon contribution:
3 carbon atoms × 12.01 g/mol = 36.03 g/mol
Hydrogen contribution:
8 hydrogen atoms × 1.008 g/mol = 8.064 g/mol
Total molar mass of C₃H₈:
36.03 g/mol + 8.064 g/mol = 44.094 g/mol
Rounded to one decimal place (as is typical in multiple-choice formats), the molar mass is:
👉 44.1 g/mol
Explanation (Approx. 300 Words):
Molar mass is a fundamental concept in chemistry, referring to the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For molecular compounds, the molar mass is found by summing the atomic masses of all atoms present in the molecular formula.
In this case, propane is a hydrocarbon with the molecular formula C₃H₈, meaning each molecule contains three carbon atoms and eight hydrogen atoms. These numbers reflect how many atoms of each element are bonded together to form one molecule of propane.
To determine the molar mass, we consult the periodic table for atomic masses:
- Carbon atoms each weigh approximately 12.01 g/mol.
- Hydrogen atoms each weigh about 1.008 g/mol.
We multiply the number of each atom in the formula by its atomic mass:
- 3 carbons × 12.01 = 36.03
- 8 hydrogens × 1.008 = 8.064
Adding these together gives a total molar mass of 44.094 g/mol, which is rounded to 44.1 g/mol for simplicity in typical chemical calculations.
Understanding molar mass is crucial for stoichiometry, which involves calculating reactant and product quantities in chemical reactions. For example, if you burn propane as fuel, you need to know its molar mass to calculate how much oxygen is required or how much carbon dioxide is produced.
Hence, the correct molar mass of propane is 44.1 g/mol, making this the correct answer.