Sucrose saccharose: molecular formula and molar mass
Sucrose and saccharose are two names for the same molecular compound (commonly called table sugar). General chemistry treatment emphasizes molecular formula, molar mass (formula mass), and mass percent composition from atomic masses.
Molecular formula and atom counts
The molecular formula of sucrose (saccharose) is C12H22O11. The subscripts indicate the atom counts in one molecule: 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms.
“Molar mass” refers to grams per mole of molecules. “Formula mass” is often used as a parallel term; for a molecular compound like sucrose, the numerical value matches the molar mass because it is built from the same atomic-mass sum.
Molar mass (formula mass) of sucrose (saccharose)
Using standard average atomic masses \(M_{\mathrm{C}} = 12.01\ \mathrm{g\cdot mol^{-1}}\), \(M_{\mathrm{H}} = 1.008\ \mathrm{g\cdot mol^{-1}}\), and \(M_{\mathrm{O}} = 16.00\ \mathrm{g\cdot mol^{-1}}\), the molar mass follows from a weighted sum:
\[ M\!\left(\mathrm{C_{12}H_{22}O_{11}}\right) = 12 \times M_{\mathrm{C}} + 22 \times M_{\mathrm{H}} + 11 \times M_{\mathrm{O}}. \] \[ M\!\left(\mathrm{C_{12}H_{22}O_{11}}\right) = 12 \times 12.01 + 22 \times 1.008 + 11 \times 16.00 = 342.30\ \mathrm{g\cdot mol^{-1}}. \]| Element | Count | Atomic mass (g·mol−1) | Contribution (g·mol−1) |
|---|---|---|---|
| Carbon (C) | 12 | 12.01 | 144.12 |
| Hydrogen (H) | 22 | 1.008 | 22.176 |
| Oxygen (O) | 11 | 16.00 | 176.00 |
| Total | — | — | 342.30 |
Percent composition by mass
Mass percent for each element follows from the fraction of the total molar mass contributed by that element: \(\%\mathrm{X} = \dfrac{\text{mass from X}}{M_{\text{total}}} \times 100\%\).
\[ \%\mathrm{C} = \frac{144.12}{342.30}\times 100\% = 42.10\% \quad \%\mathrm{H} = \frac{22.176}{342.30}\times 100\% = 6.48\% \quad \%\mathrm{O} = \frac{176.00}{342.30}\times 100\% = 51.42\%. \]Common pitfalls
Confusion between “molecular formula” and “empirical formula” can arise; sucrose has molecular formula C12H22O11, and no simpler whole-number ratio reduces it. Arithmetic slips commonly come from missing a subscript, mixing atomic masses with different rounding conventions, or omitting units on the final molar mass.
Key results
Sucrose (saccharose) has molecular formula C12H22O11 and molar mass \(342.30\ \mathrm{g\cdot mol^{-1}}\), with percent composition approximately 42.10% C, 6.48% H, and 51.42% O.