mass fractions of vanadium(IV) fluoride

vanadium(IV) fluoride | elemental composition

Find the elemental composition for vanadium(IV) fluoride 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: VF_4 Use the chemical formula, VF_4, to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms: | number of atoms F (fluorine) | 4 V (vanadium) | 1 N_atoms = 4 + 1 = 5 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 F (fluorine) | 4 | 4/5 V (vanadium) | 1 | 1/5 Check: 4/5 + 1/5 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent F (fluorine) | 4 | 4/5 × 100% = 80.0% V (vanadium) | 1 | 1/5 × 100% = 20.0% 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 F (fluorine) | 4 | 80.0% | 18.998403163 V (vanadium) | 1 | 20.0% | 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 F (fluorine) | 4 | 80.0% | 18.998403163 | 4 × 18.998403163 = 75.993612652 V (vanadium) | 1 | 20.0% | 50.9415 | 1 × 50.9415 = 50.9415 m = 75.993612652 u + 50.9415 u = 126.935112652 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 F (fluorine) | 4 | 80.0% | 75.993612652/126.935112652 V (vanadium) | 1 | 20.0% | 50.9415/126.935112652 Check: 75.993612652/126.935112652 + 50.9415/126.935112652 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent F (fluorine) | 4 | 80.0% | 75.993612652/126.935112652 × 100% = 59.87% V (vanadium) | 1 | 20.0% | 50.9415/126.935112652 × 100% = 40.13%

Mass fraction pie chart