mass fractions of 2'-deoxyadenosine

2'-deoxyadenosine | elemental composition

Find the elemental composition for 2'-deoxyadenosine 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_10H_13N_5O_3·H_2O Use the chemical formula, C_10H_13N_5O_3·H_2O, 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) | 10 H (hydrogen) | 13 N (nitrogen) | 5 O (oxygen) | 3 N_atoms = 10 + 13 + 5 + 3 = 31 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) | 10 | 10/31 H (hydrogen) | 13 | 13/31 N (nitrogen) | 5 | 5/31 O (oxygen) | 3 | 3/31 Check: 10/31 + 13/31 + 5/31 + 3/31 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 10 | 10/31 × 100% = 32.3% H (hydrogen) | 13 | 13/31 × 100% = 41.9% N (nitrogen) | 5 | 5/31 × 100% = 16.1% O (oxygen) | 3 | 3/31 × 100% = 9.68% 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) | 10 | 32.3% | 12.011 H (hydrogen) | 13 | 41.9% | 1.008 N (nitrogen) | 5 | 16.1% | 14.007 O (oxygen) | 3 | 9.68% | 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) | 10 | 32.3% | 12.011 | 10 × 12.011 = 120.110 H (hydrogen) | 13 | 41.9% | 1.008 | 13 × 1.008 = 13.104 N (nitrogen) | 5 | 16.1% | 14.007 | 5 × 14.007 = 70.035 O (oxygen) | 3 | 9.68% | 15.999 | 3 × 15.999 = 47.997 m = 120.110 u + 13.104 u + 70.035 u + 47.997 u = 251.246 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) | 10 | 32.3% | 120.110/251.246 H (hydrogen) | 13 | 41.9% | 13.104/251.246 N (nitrogen) | 5 | 16.1% | 70.035/251.246 O (oxygen) | 3 | 9.68% | 47.997/251.246 Check: 120.110/251.246 + 13.104/251.246 + 70.035/251.246 + 47.997/251.246 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 10 | 32.3% | 120.110/251.246 × 100% = 47.81% H (hydrogen) | 13 | 41.9% | 13.104/251.246 × 100% = 5.216% N (nitrogen) | 5 | 16.1% | 70.035/251.246 × 100% = 27.88% O (oxygen) | 3 | 9.68% | 47.997/251.246 × 100% = 19.10%

Mass fraction pie chart