mass fractions of mercury oleate

mercury oleate | elemental composition

Find the elemental composition for mercury oleate in terms of the atom and mass percents: atom percent = N_i/N_atoms × 100% mass percent = (N_im_i)/m × 100% Plan: • Write the chemical formula and gather atomic masses from the periodic table. • Determine values for N_i, m_i, N_atoms and m using these items. • Finally, compute the percents and check the results. Write the chemical formula: C_36H_66HgO_4 Use the chemical formula to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms, per molecule: | number of atoms C (carbon) | 36 H (hydrogen) | 66 Hg (mercury) | 1 O (oxygen) | 4 N_atoms = 36 + 66 + 1 + 4 = 107 Divide each N_i by N_atoms to calculate atom fractions. Then use the property that atom fractions must sum to one to check the work: | number of atoms | atom fraction C (carbon) | 36 | 36/107 H (hydrogen) | 66 | 66/107 Hg (mercury) | 1 | 1/107 O (oxygen) | 4 | 4/107 Check: 36/107 + 66/107 + 1/107 + 4/107 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 36 | 36/107 × 100% = 33.6% H (hydrogen) | 66 | 66/107 × 100% = 61.7% Hg (mercury) | 1 | 1/107 × 100% = 0.935% O (oxygen) | 4 | 4/107 × 100% = 3.74% Look up the atomic mass, m_i, in unified atomic mass units, u, for each element in the periodic table: | number of atoms | atom percent | atomic mass/u C (carbon) | 36 | 33.6% | 12.011 H (hydrogen) | 66 | 61.7% | 1.008 Hg (mercury) | 1 | 0.935% | 200.592 O (oxygen) | 4 | 3.74% | 15.999 Multiply N_i by m_i to compute the mass for each element. Then sum those values to compute the molecular mass, m: | number of atoms | atom percent | atomic mass/u | mass/u C (carbon) | 36 | 33.6% | 12.011 | 36 × 12.011 = 432.396 H (hydrogen) | 66 | 61.7% | 1.008 | 66 × 1.008 = 66.528 Hg (mercury) | 1 | 0.935% | 200.592 | 1 × 200.592 = 200.592 O (oxygen) | 4 | 3.74% | 15.999 | 4 × 15.999 = 63.996 m = 432.396 u + 66.528 u + 200.592 u + 63.996 u = 763.512 u Divide the mass for each element by m to calculate mass fractions. Then use the property that mass fractions must sum to one to check the work: | number of atoms | atom percent | mass fraction C (carbon) | 36 | 33.6% | 432.396/763.512 H (hydrogen) | 66 | 61.7% | 66.528/763.512 Hg (mercury) | 1 | 0.935% | 200.592/763.512 O (oxygen) | 4 | 3.74% | 63.996/763.512 Check: 432.396/763.512 + 66.528/763.512 + 200.592/763.512 + 63.996/763.512 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 36 | 33.6% | 432.396/763.512 × 100% = 56.63% H (hydrogen) | 66 | 61.7% | 66.528/763.512 × 100% = 8.713% Hg (mercury) | 1 | 0.935% | 200.592/763.512 × 100% = 26.27% O (oxygen) | 4 | 3.74% | 63.996/763.512 × 100% = 8.382%

Mass fraction pie chart