relative molecular mass of [5,6]-fullerene-C70

[5, 6]-fullerene-C70 | relative molecular mass

Find the relative molecular mass, M_r, for [5, 6]-fullerene-C70: 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_70 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i C (carbon) | 70 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) | 70 | 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) | 70 | 12.011 | 70 × 12.011 = 840.770 M_r = 840.770

≈ 1.2 × relative molecular mass of fullerene ( ≈ 721 )

≈ 4.3 × relative molecular mass of caffeine ( ≈ 194 )

≈ 14 × relative molecular mass of sodium chloride ( ≈ 58 )

Molar mass M from M = M_uM_r: | 841 g/mol (grams per mole)

Molecular mass m from m = M_rM_u/N_A: | 1.4×10^-21 grams | 1.4×10^-24 kg (kilograms)