What is the molar mass of heptane?
The correct answer and explanation is:
The molar mass of heptane (C7H16) is approximately 100.21 grams per mole.
Heptane is an alkane with the chemical formula C7H16, meaning it contains 7 carbon atoms and 16 hydrogen atoms. To calculate its molar mass, add the total mass contributed by all the carbon atoms to the total mass contributed by all the hydrogen atoms.
Each carbon atom has an atomic mass of about 12.01 grams per mole, and each hydrogen atom has an atomic mass of approximately 1.008 grams per mole. Multiply the number of each atom by its atomic mass:
- Carbon: 7 atoms × 12.01 g/mol = 84.07 g/mol
- Hydrogen: 16 atoms × 1.008 g/mol = 16.13 g/mol
Adding these together gives the molar mass of heptane:
84.07 g/mol + 16.13 g/mol = 100.20 g/mol
Rounding slightly, the molar mass is 100.21 g/mol.
The molar mass is important in chemistry because it relates the mass of a substance to the amount of substance in moles. This allows calculations involving mass-to-mole conversions, determining the amount of substance in a sample, or preparing solutions of known concentration.
Heptane is a hydrocarbon used often as a solvent and reference standard in octane rating tests for fuels. Its molecular weight affects physical properties such as boiling point, density, and volatility.
When dealing with molecular formulas, the calculation of molar mass is a straightforward process of multiplying atomic masses by the number of atoms and summing them. This method applies to any compound once its formula is known.
In summary, the molar mass of heptane is about 100.21 grams per mole, calculated from the sum of the masses of 7 carbon and 16 hydrogen atoms. This value is used frequently in chemistry for stoichiometric calculations and understanding physical properties.