mass fractions of iodoacetonitrile

iodoacetonitrile | elemental composition

Find the elemental composition for iodoacetonitrile 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_2CN 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) | 2 H (hydrogen) | 2 I (iodine) | 1 N (nitrogen) | 1 N_atoms = 2 + 2 + 1 + 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 C (carbon) | 2 | 2/6 H (hydrogen) | 2 | 2/6 I (iodine) | 1 | 1/6 N (nitrogen) | 1 | 1/6 Check: 2/6 + 2/6 + 1/6 + 1/6 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 2 | 2/6 × 100% = 33.3% H (hydrogen) | 2 | 2/6 × 100% = 33.3% I (iodine) | 1 | 1/6 × 100% = 16.7% N (nitrogen) | 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 C (carbon) | 2 | 33.3% | 12.011 H (hydrogen) | 2 | 33.3% | 1.008 I (iodine) | 1 | 16.7% | 126.90447 N (nitrogen) | 1 | 16.7% | 14.007 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 | 33.3% | 12.011 | 2 × 12.011 = 24.022 H (hydrogen) | 2 | 33.3% | 1.008 | 2 × 1.008 = 2.016 I (iodine) | 1 | 16.7% | 126.90447 | 1 × 126.90447 = 126.90447 N (nitrogen) | 1 | 16.7% | 14.007 | 1 × 14.007 = 14.007 m = 24.022 u + 2.016 u + 126.90447 u + 14.007 u = 166.94947 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 | 33.3% | 24.022/166.94947 H (hydrogen) | 2 | 33.3% | 2.016/166.94947 I (iodine) | 1 | 16.7% | 126.90447/166.94947 N (nitrogen) | 1 | 16.7% | 14.007/166.94947 Check: 24.022/166.94947 + 2.016/166.94947 + 126.90447/166.94947 + 14.007/166.94947 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 2 | 33.3% | 24.022/166.94947 × 100% = 14.39% H (hydrogen) | 2 | 33.3% | 2.016/166.94947 × 100% = 1.208% I (iodine) | 1 | 16.7% | 126.90447/166.94947 × 100% = 76.01% N (nitrogen) | 1 | 16.7% | 14.007/166.94947 × 100% = 8.390%

Mass fraction pie chart