mass fractions of 4-iodo-3-nitrotoluene

4-iodo-3-nitrotoluene | elemental composition

Find the elemental composition for 4-iodo-3-nitrotoluene 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: IC_6H_3(CH_3)NO_2 Use the chemical formula, IC_6H_3(CH_3)NO_2, 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) | 7 H (hydrogen) | 6 I (iodine) | 1 N (nitrogen) | 1 O (oxygen) | 2 N_atoms = 7 + 6 + 1 + 1 + 2 = 17 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) | 7 | 7/17 H (hydrogen) | 6 | 6/17 I (iodine) | 1 | 1/17 N (nitrogen) | 1 | 1/17 O (oxygen) | 2 | 2/17 Check: 7/17 + 6/17 + 1/17 + 1/17 + 2/17 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 7 | 7/17 × 100% = 41.2% H (hydrogen) | 6 | 6/17 × 100% = 35.3% I (iodine) | 1 | 1/17 × 100% = 5.88% N (nitrogen) | 1 | 1/17 × 100% = 5.88% O (oxygen) | 2 | 2/17 × 100% = 11.8% 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) | 7 | 41.2% | 12.011 H (hydrogen) | 6 | 35.3% | 1.008 I (iodine) | 1 | 5.88% | 126.90447 N (nitrogen) | 1 | 5.88% | 14.007 O (oxygen) | 2 | 11.8% | 15.999 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) | 7 | 41.2% | 12.011 | 7 × 12.011 = 84.077 H (hydrogen) | 6 | 35.3% | 1.008 | 6 × 1.008 = 6.048 I (iodine) | 1 | 5.88% | 126.90447 | 1 × 126.90447 = 126.90447 N (nitrogen) | 1 | 5.88% | 14.007 | 1 × 14.007 = 14.007 O (oxygen) | 2 | 11.8% | 15.999 | 2 × 15.999 = 31.998 m = 84.077 u + 6.048 u + 126.90447 u + 14.007 u + 31.998 u = 263.03447 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) | 7 | 41.2% | 84.077/263.03447 H (hydrogen) | 6 | 35.3% | 6.048/263.03447 I (iodine) | 1 | 5.88% | 126.90447/263.03447 N (nitrogen) | 1 | 5.88% | 14.007/263.03447 O (oxygen) | 2 | 11.8% | 31.998/263.03447 Check: 84.077/263.03447 + 6.048/263.03447 + 126.90447/263.03447 + 14.007/263.03447 + 31.998/263.03447 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 7 | 41.2% | 84.077/263.03447 × 100% = 31.96% H (hydrogen) | 6 | 35.3% | 6.048/263.03447 × 100% = 2.299% I (iodine) | 1 | 5.88% | 126.90447/263.03447 × 100% = 48.25% N (nitrogen) | 1 | 5.88% | 14.007/263.03447 × 100% = 5.325% O (oxygen) | 2 | 11.8% | 31.998/263.03447 × 100% = 12.16%

Mass fraction pie chart