element mass fraction of tritriacontanol

tritriacontanol | elemental composition

Find the elemental composition for tritriacontanol 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_33H_68O_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 C (carbon) | 33 H (hydrogen) | 68 O (oxygen) | 1 N_atoms = 33 + 68 + 1 = 102 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) | 33 | 33/102 H (hydrogen) | 68 | 68/102 O (oxygen) | 1 | 1/102 Check: 33/102 + 68/102 + 1/102 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 33 | 33/102 × 100% = 32.4% H (hydrogen) | 68 | 68/102 × 100% = 66.7% O (oxygen) | 1 | 1/102 × 100% = 0.980% 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) | 33 | 32.4% | 12.011 H (hydrogen) | 68 | 66.7% | 1.008 O (oxygen) | 1 | 0.980% | 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) | 33 | 32.4% | 12.011 | 33 × 12.011 = 396.363 H (hydrogen) | 68 | 66.7% | 1.008 | 68 × 1.008 = 68.544 O (oxygen) | 1 | 0.980% | 15.999 | 1 × 15.999 = 15.999 m = 396.363 u + 68.544 u + 15.999 u = 480.906 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) | 33 | 32.4% | 396.363/480.906 H (hydrogen) | 68 | 66.7% | 68.544/480.906 O (oxygen) | 1 | 0.980% | 15.999/480.906 Check: 396.363/480.906 + 68.544/480.906 + 15.999/480.906 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 33 | 32.4% | 396.363/480.906 × 100% = 82.42% H (hydrogen) | 68 | 66.7% | 68.544/480.906 × 100% = 14.25% O (oxygen) | 1 | 0.980% | 15.999/480.906 × 100% = 3.327%

Mass fraction pie chart