Input interpretation
2-(1, 3-dioxolan-2-yl)ethyltriphenylphosphonium bromide | relative molecular mass
Result
Find the relative molecular mass, M_r, for 2-(1, 3-dioxolan-2-yl)ethyltriphenylphosphonium bromide: 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_23H_24BrO_2P Use the chemical formula to count the number of atoms, N_i, for each element: | N_i Br (bromine) | 1 O (oxygen) | 2 C (carbon) | 23 P (phosphorus) | 1 H (hydrogen) | 24 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 Br (bromine) | 1 | 79.904 O (oxygen) | 2 | 15.999 C (carbon) | 23 | 12.011 P (phosphorus) | 1 | 30.973761998 H (hydrogen) | 24 | 1.008 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 Br (bromine) | 1 | 79.904 | 1 × 79.904 = 79.904 O (oxygen) | 2 | 15.999 | 2 × 15.999 = 31.998 C (carbon) | 23 | 12.011 | 23 × 12.011 = 276.253 P (phosphorus) | 1 | 30.973761998 | 1 × 30.973761998 = 30.973761998 H (hydrogen) | 24 | 1.008 | 24 × 1.008 = 24.192 M_r = 79.904 + 31.998 + 276.253 + 30.973761998 + 24.192 = 443.321
Comparisons
≈ 0.62 × relative molecular mass of fullerene ( ≈ 721 )
≈ 2.3 × relative molecular mass of caffeine ( ≈ 194 )
≈ 7.6 × relative molecular mass of sodium chloride ( ≈ 58 )
Corresponding quantities
Molar mass M from M = M_uM_r: | 443 g/mol (grams per mole)
Molecular mass m from m = M_rM_u/N_A: | 7.4×10^-22 grams | 7.4×10^-25 kg (kilograms)