element mass fraction of vanadyl sulfate

vanadyl sulfate | elemental composition

Find the elemental composition for vanadyl sulfate 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: VOSO_4·2H_2O 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 O (oxygen) | 5 S (sulfur) | 1 V (vanadium) | 1 N_atoms = 5 + 1 + 1 = 7 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 O (oxygen) | 5 | 5/7 S (sulfur) | 1 | 1/7 V (vanadium) | 1 | 1/7 Check: 5/7 + 1/7 + 1/7 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent O (oxygen) | 5 | 5/7 × 100% = 71.4% S (sulfur) | 1 | 1/7 × 100% = 14.3% V (vanadium) | 1 | 1/7 × 100% = 14.3% 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 O (oxygen) | 5 | 71.4% | 15.999 S (sulfur) | 1 | 14.3% | 32.06 V (vanadium) | 1 | 14.3% | 50.9415 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 O (oxygen) | 5 | 71.4% | 15.999 | 5 × 15.999 = 79.995 S (sulfur) | 1 | 14.3% | 32.06 | 1 × 32.06 = 32.06 V (vanadium) | 1 | 14.3% | 50.9415 | 1 × 50.9415 = 50.9415 m = 79.995 u + 32.06 u + 50.9415 u = 162.9965 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 O (oxygen) | 5 | 71.4% | 79.995/162.9965 S (sulfur) | 1 | 14.3% | 32.06/162.9965 V (vanadium) | 1 | 14.3% | 50.9415/162.9965 Check: 79.995/162.9965 + 32.06/162.9965 + 50.9415/162.9965 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent O (oxygen) | 5 | 71.4% | 79.995/162.9965 × 100% = 49.08% S (sulfur) | 1 | 14.3% | 32.06/162.9965 × 100% = 19.67% V (vanadium) | 1 | 14.3% | 50.9415/162.9965 × 100% = 31.25%

Mass fraction pie chart