Input interpretation
buckminsterfullerene | relative molecular mass
Result
Find the relative molecular mass, M_r, for buckminsterfullerene: M_r = sum _iN_im_i/m_u 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: C_60 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i C (carbon) | 60 Look up the atomic mass, m_i, in unified atomic mass units, u, for each element in the periodic table. Since m_i is divided by the atomic mass constant, m_u, the result is a unitless relative atomic mass: | N_i | m_i/m_u C (carbon) | 60 | 12.011 Multiply N_i by m_i/m_u to compute the relative mass for each element. Then sum those values to compute the relative molecular mass, M_r: Answer: | | | N_i | m_i/m_u | relative mass C (carbon) | 60 | 12.011 | 60 × 12.011 = 720.660 M_r = 720.660
Comparisons
≈ 3.7 × relative molecular mass of caffeine ( ≈ 194 )
≈ 12 × relative molecular mass of sodium chloride ( ≈ 58 )
≈ 40 × relative molecular mass of water ( ≈ 18 )
Corresponding quantities
Molar mass M from M = M_uM_r: | 721 g/mol (grams per mole)
Molecular mass m from m = M_rM_u/N_A: | 1.2×10^-21 grams | 1.2×10^-24 kg (kilograms)