mass fractions of 2-ethylhexyl acrylate

2-ethylhexyl acrylate | elemental composition

Find the elemental composition for 2-ethylhexyl acrylate 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: CH_2=CHCOOCH_2CH(C_2H_5)(CH_2)_3CH_3 Use the chemical formula, CH_2=CHCOOCH_2CH(C_2H_5)(CH_2)_3CH_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) | 11 H (hydrogen) | 20 O (oxygen) | 2 N_atoms = 11 + 20 + 2 = 33 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) | 11 | 11/33 H (hydrogen) | 20 | 20/33 O (oxygen) | 2 | 2/33 Check: 11/33 + 20/33 + 2/33 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 11 | 11/33 × 100% = 33.3% H (hydrogen) | 20 | 20/33 × 100% = 60.6% O (oxygen) | 2 | 2/33 × 100% = 6.06% 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) | 11 | 33.3% | 12.011 H (hydrogen) | 20 | 60.6% | 1.008 O (oxygen) | 2 | 6.06% | 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) | 11 | 33.3% | 12.011 | 11 × 12.011 = 132.121 H (hydrogen) | 20 | 60.6% | 1.008 | 20 × 1.008 = 20.160 O (oxygen) | 2 | 6.06% | 15.999 | 2 × 15.999 = 31.998 m = 132.121 u + 20.160 u + 31.998 u = 184.279 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) | 11 | 33.3% | 132.121/184.279 H (hydrogen) | 20 | 60.6% | 20.160/184.279 O (oxygen) | 2 | 6.06% | 31.998/184.279 Check: 132.121/184.279 + 20.160/184.279 + 31.998/184.279 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 11 | 33.3% | 132.121/184.279 × 100% = 71.70% H (hydrogen) | 20 | 60.6% | 20.160/184.279 × 100% = 10.94% O (oxygen) | 2 | 6.06% | 31.998/184.279 × 100% = 17.36%

Mass fraction pie chart