mass fractions of iodine pentafluoride

iodine pentafluoride | elemental composition

Find the elemental composition for iodine pentafluoride 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: F_5I_1 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 F (fluorine) | 5 I (iodine) | 1 N_atoms = 5 + 1 = 6 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) | 5 | 5/6 I (iodine) | 1 | 1/6 Check: 5/6 + 1/6 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent F (fluorine) | 5 | 5/6 × 100% = 83.3% I (iodine) | 1 | 1/6 × 100% = 16.7% 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) | 5 | 83.3% | 18.998403163 I (iodine) | 1 | 16.7% | 126.90447 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) | 5 | 83.3% | 18.998403163 | 5 × 18.998403163 = 94.992015815 I (iodine) | 1 | 16.7% | 126.90447 | 1 × 126.90447 = 126.90447 m = 94.992015815 u + 126.90447 u = 221.896485815 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) | 5 | 83.3% | 94.992015815/221.896485815 I (iodine) | 1 | 16.7% | 126.90447/221.896485815 Check: 94.992015815/221.896485815 + 126.90447/221.896485815 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent F (fluorine) | 5 | 83.3% | 94.992015815/221.896485815 × 100% = 42.81% I (iodine) | 1 | 16.7% | 126.90447/221.896485815 × 100% = 57.19%

Mass fraction pie chart