Input interpretation
diborane | molecular mass
Result
Find the molecular mass, m, for diborane: 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: B_2H_6 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i B (boron) | 2 H (hydrogen) | 6 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 B (boron) | 2 | 10.81 H (hydrogen) | 6 | 1.008 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 B (boron) | 2 | 10.81 | 2 × 10.81 = 21.62 H (hydrogen) | 6 | 1.008 | 6 × 1.008 = 6.048 m = 21.62 u + 6.048 u = 27.67 u
Unit conversions
27.67 Da (daltons)
0.02767 kDa (kilodaltons)
4.594×10^-23 grams
4.594×10^-26 kg (kilograms)
27.67 chemical atomic mass units (unit officially deprecated)
27.68 physical atomic mass units (unit officially deprecated)
Comparisons as mass of molecule
≈ ( 0.14 ≈ 1/7 ) × molecular mass of caffeine ( ≈ 194 u )
≈ 0.47 × molecular mass of sodium chloride ( ≈ 58 u )
≈ 1.5 × molecular mass of water ( ≈ 18 u )
Corresponding quantities
Relative atomic mass A_r from A_r = m_aN_A/M_u: | 28
Molar mass M from M = m_aN_A: | 28 g/mol (grams per mole)
Relative molecular mass M_r from M_r = m_mN_A/M_u: | 28
Molar mass M from M = m_mN_A: | 28 g/mol (grams per mole)