Input interpretation
diborane | molar mass
Result
Find the molar 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 g·mol^(-1) for each element in the periodic table: | N_i | m_i/g·mol^(-1) 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 molar mass, M: Answer: | | | N_i | m_i/g·mol^(-1) | mass/g·mol^(-1) B (boron) | 2 | 10.81 | 2 × 10.81 = 21.62 H (hydrogen) | 6 | 1.008 | 6 × 1.008 = 6.048 M = 21.62 g/mol + 6.048 g/mol = 27.67 g/mol
Unit conversion
0.02767 kg/mol (kilograms per mole)
Comparisons
≈ ( 0.14 ≈ 1/7 ) × molar mass of caffeine ( ≈ 194 g/mol )
≈ 0.47 × molar mass of sodium chloride ( ≈ 58 g/mol )
≈ 1.5 × molar mass of water ( ≈ 18 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 4.6×10^-23 grams | 4.6×10^-26 kg (kilograms) | 28 u (unified atomic mass units) | 28 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 28