mass fractions of 1,2-diiodoethane

1, 2-diiodoethane | elemental composition

Find the elemental composition for 1, 2-diiodoethane 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: ICH_2CH_2I Use the chemical formula, ICH_2CH_2I, to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms: | number of atoms C (carbon) | 2 H (hydrogen) | 4 I (iodine) | 2 N_atoms = 2 + 4 + 2 = 8 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) | 2 | 2/8 H (hydrogen) | 4 | 4/8 I (iodine) | 2 | 2/8 Check: 2/8 + 4/8 + 2/8 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 2 | 2/8 × 100% = 25.0% H (hydrogen) | 4 | 4/8 × 100% = 50.0% I (iodine) | 2 | 2/8 × 100% = 25.0% 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 C (carbon) | 2 | 25.0% | 12.011 H (hydrogen) | 4 | 50.0% | 1.008 I (iodine) | 2 | 25.0% | 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 C (carbon) | 2 | 25.0% | 12.011 | 2 × 12.011 = 24.022 H (hydrogen) | 4 | 50.0% | 1.008 | 4 × 1.008 = 4.032 I (iodine) | 2 | 25.0% | 126.90447 | 2 × 126.90447 = 253.80894 m = 24.022 u + 4.032 u + 253.80894 u = 281.86294 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) | 2 | 25.0% | 24.022/281.86294 H (hydrogen) | 4 | 50.0% | 4.032/281.86294 I (iodine) | 2 | 25.0% | 253.80894/281.86294 Check: 24.022/281.86294 + 4.032/281.86294 + 253.80894/281.86294 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 2 | 25.0% | 24.022/281.86294 × 100% = 8.523% H (hydrogen) | 4 | 50.0% | 4.032/281.86294 × 100% = 1.430% I (iodine) | 2 | 25.0% | 253.80894/281.86294 × 100% = 90.05%

Mass fraction pie chart