mass fractions of 1-(2,3,4,5,6-pentafluorophenyl)-1-propanol

1-(2, 3, 4, 5, 6-pentafluorophenyl)-1-propanol | elemental composition

Find the elemental composition for 1-(2, 3, 4, 5, 6-pentafluorophenyl)-1-propanol 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: C_6F_5CHOHCH_2CH_3 Use the chemical formula, C_6F_5CHOHCH_2CH_3, 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) | 9 F (fluorine) | 5 H (hydrogen) | 7 O (oxygen) | 1 N_atoms = 9 + 5 + 7 + 1 = 22 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) | 9 | 9/22 F (fluorine) | 5 | 5/22 H (hydrogen) | 7 | 7/22 O (oxygen) | 1 | 1/22 Check: 9/22 + 5/22 + 7/22 + 1/22 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 9 | 9/22 × 100% = 40.9% F (fluorine) | 5 | 5/22 × 100% = 22.7% H (hydrogen) | 7 | 7/22 × 100% = 31.8% O (oxygen) | 1 | 1/22 × 100% = 4.55% 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) | 9 | 40.9% | 12.011 F (fluorine) | 5 | 22.7% | 18.998403163 H (hydrogen) | 7 | 31.8% | 1.008 O (oxygen) | 1 | 4.55% | 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) | 9 | 40.9% | 12.011 | 9 × 12.011 = 108.099 F (fluorine) | 5 | 22.7% | 18.998403163 | 5 × 18.998403163 = 94.992015815 H (hydrogen) | 7 | 31.8% | 1.008 | 7 × 1.008 = 7.056 O (oxygen) | 1 | 4.55% | 15.999 | 1 × 15.999 = 15.999 m = 108.099 u + 94.992015815 u + 7.056 u + 15.999 u = 226.146015815 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) | 9 | 40.9% | 108.099/226.146015815 F (fluorine) | 5 | 22.7% | 94.992015815/226.146015815 H (hydrogen) | 7 | 31.8% | 7.056/226.146015815 O (oxygen) | 1 | 4.55% | 15.999/226.146015815 Check: 108.099/226.146015815 + 94.992015815/226.146015815 + 7.056/226.146015815 + 15.999/226.146015815 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 9 | 40.9% | 108.099/226.146015815 × 100% = 47.80% F (fluorine) | 5 | 22.7% | 94.992015815/226.146015815 × 100% = 42.00% H (hydrogen) | 7 | 31.8% | 7.056/226.146015815 × 100% = 3.120% O (oxygen) | 1 | 4.55% | 15.999/226.146015815 × 100% = 7.075%

Mass fraction pie chart