Input interpretation
ethanol | molecular mass
Result
Find the molecular mass, m, for ethanol: m = sum _iN_im_i Plan: • Write the chemical formula and gather atomic masses from the periodic table. • Determine values for N_i and m_i using these items. • Finally, compute the mass. Write the chemical formula: CH_3CH_2OH Use the chemical formula, CH_3CH_2OH, to count the number of atoms, N_i, for each element: | N_i C (carbon) | 2 H (hydrogen) | 6 O (oxygen) | 1 Look up the atomic mass, m_i, in unified atomic mass units, u, for each element in the periodic table: | N_i | m_i/u C (carbon) | 2 | 12.011 H (hydrogen) | 6 | 1.008 O (oxygen) | 1 | 15.999 Multiply N_i by m_i to compute the mass for each element. Then sum those values to compute the molecular mass, m: Answer: | | | N_i | m_i/u | mass/u C (carbon) | 2 | 12.011 | 2 × 12.011 = 24.022 H (hydrogen) | 6 | 1.008 | 6 × 1.008 = 6.048 O (oxygen) | 1 | 15.999 | 1 × 15.999 = 15.999 m = 24.022 u + 6.048 u + 15.999 u = 46.069 u
Unit conversions
46.07 Da (daltons)
0.04607 kDa (kilodaltons)
7.65×10^-23 grams
7.65×10^-26 kg (kilograms)
46.07 chemical atomic mass units (unit officially deprecated)
46.08 physical atomic mass units (unit officially deprecated)
Comparisons as mass of molecule
≈ ( 0.064 ≈ 1/16 ) × molecular mass of fullerene ( ≈ 721 u )
≈ ( 0.24 ≈ 1/4 ) × molecular mass of caffeine ( ≈ 194 u )
≈ 0.79 × molecular mass of sodium chloride ( ≈ 58 u )
Corresponding quantities
Relative atomic mass A_r from A_r = m_aN_A/M_u: | 46
Molar mass M from M = m_aN_A: | 46 g/mol (grams per mole)
Relative molecular mass M_r from M_r = m_mN_A/M_u: | 46
Molar mass M from M = m_mN_A: | 46 g/mol (grams per mole)