mass fractions of lithium p-toluenesulfinate

lithium p-toluenesulfinate | elemental composition

Find the elemental composition for lithium p-toluenesulfinate 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: CH_3C_6H_4SO_2Li 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) | 7 H (hydrogen) | 7 Li (lithium) | 1 O (oxygen) | 2 S (sulfur) | 1 N_atoms = 7 + 7 + 1 + 2 + 1 = 18 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) | 7 | 7/18 H (hydrogen) | 7 | 7/18 Li (lithium) | 1 | 1/18 O (oxygen) | 2 | 2/18 S (sulfur) | 1 | 1/18 Check: 7/18 + 7/18 + 1/18 + 2/18 + 1/18 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 7 | 7/18 × 100% = 38.9% H (hydrogen) | 7 | 7/18 × 100% = 38.9% Li (lithium) | 1 | 1/18 × 100% = 5.56% O (oxygen) | 2 | 2/18 × 100% = 11.1% S (sulfur) | 1 | 1/18 × 100% = 5.56% 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) | 7 | 38.9% | 12.011 H (hydrogen) | 7 | 38.9% | 1.008 Li (lithium) | 1 | 5.56% | 6.94 O (oxygen) | 2 | 11.1% | 15.999 S (sulfur) | 1 | 5.56% | 32.06 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) | 7 | 38.9% | 12.011 | 7 × 12.011 = 84.077 H (hydrogen) | 7 | 38.9% | 1.008 | 7 × 1.008 = 7.056 Li (lithium) | 1 | 5.56% | 6.94 | 1 × 6.94 = 6.94 O (oxygen) | 2 | 11.1% | 15.999 | 2 × 15.999 = 31.998 S (sulfur) | 1 | 5.56% | 32.06 | 1 × 32.06 = 32.06 m = 84.077 u + 7.056 u + 6.94 u + 31.998 u + 32.06 u = 162.131 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) | 7 | 38.9% | 84.077/162.131 H (hydrogen) | 7 | 38.9% | 7.056/162.131 Li (lithium) | 1 | 5.56% | 6.94/162.131 O (oxygen) | 2 | 11.1% | 31.998/162.131 S (sulfur) | 1 | 5.56% | 32.06/162.131 Check: 84.077/162.131 + 7.056/162.131 + 6.94/162.131 + 31.998/162.131 + 32.06/162.131 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 7 | 38.9% | 84.077/162.131 × 100% = 51.86% H (hydrogen) | 7 | 38.9% | 7.056/162.131 × 100% = 4.352% Li (lithium) | 1 | 5.56% | 6.94/162.131 × 100% = 4.28% O (oxygen) | 2 | 11.1% | 31.998/162.131 × 100% = 19.74% S (sulfur) | 1 | 5.56% | 32.06/162.131 × 100% = 19.77%

Mass fraction pie chart