element counts of lucifer yellow cH

lucifer yellow cH | elemental composition

Find the elemental composition for lucifer yellow cH 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_13H_9Li_2N_5O_9S_2 Use the chemical formula, C_13H_9Li_2N_5O_9S_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) | 13 H (hydrogen) | 9 Li (lithium) | 2 N (nitrogen) | 5 O (oxygen) | 9 S (sulfur) | 2 N_atoms = 13 + 9 + 2 + 5 + 9 + 2 = 40 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) | 13 | 13/40 H (hydrogen) | 9 | 9/40 Li (lithium) | 2 | 2/40 N (nitrogen) | 5 | 5/40 O (oxygen) | 9 | 9/40 S (sulfur) | 2 | 2/40 Check: 13/40 + 9/40 + 2/40 + 5/40 + 9/40 + 2/40 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 13 | 13/40 × 100% = 32.5% H (hydrogen) | 9 | 9/40 × 100% = 22.5% Li (lithium) | 2 | 2/40 × 100% = 5.00% N (nitrogen) | 5 | 5/40 × 100% = 12.5% O (oxygen) | 9 | 9/40 × 100% = 22.5% S (sulfur) | 2 | 2/40 × 100% = 5.00% 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) | 13 | 32.5% | 12.011 H (hydrogen) | 9 | 22.5% | 1.008 Li (lithium) | 2 | 5.00% | 6.94 N (nitrogen) | 5 | 12.5% | 14.007 O (oxygen) | 9 | 22.5% | 15.999 S (sulfur) | 2 | 5.00% | 32.06 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) | 13 | 32.5% | 12.011 | 13 × 12.011 = 156.143 H (hydrogen) | 9 | 22.5% | 1.008 | 9 × 1.008 = 9.072 Li (lithium) | 2 | 5.00% | 6.94 | 2 × 6.94 = 13.88 N (nitrogen) | 5 | 12.5% | 14.007 | 5 × 14.007 = 70.035 O (oxygen) | 9 | 22.5% | 15.999 | 9 × 15.999 = 143.991 S (sulfur) | 2 | 5.00% | 32.06 | 2 × 32.06 = 64.12 m = 156.143 u + 9.072 u + 13.88 u + 70.035 u + 143.991 u + 64.12 u = 457.241 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) | 13 | 32.5% | 156.143/457.241 H (hydrogen) | 9 | 22.5% | 9.072/457.241 Li (lithium) | 2 | 5.00% | 13.88/457.241 N (nitrogen) | 5 | 12.5% | 70.035/457.241 O (oxygen) | 9 | 22.5% | 143.991/457.241 S (sulfur) | 2 | 5.00% | 64.12/457.241 Check: 156.143/457.241 + 9.072/457.241 + 13.88/457.241 + 70.035/457.241 + 143.991/457.241 + 64.12/457.241 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 13 | 32.5% | 156.143/457.241 × 100% = 34.15% H (hydrogen) | 9 | 22.5% | 9.072/457.241 × 100% = 1.984% Li (lithium) | 2 | 5.00% | 13.88/457.241 × 100% = 3.04% N (nitrogen) | 5 | 12.5% | 70.035/457.241 × 100% = 15.32% O (oxygen) | 9 | 22.5% | 143.991/457.241 × 100% = 31.49% S (sulfur) | 2 | 5.00% | 64.12/457.241 × 100% = 14.02%

Mass fraction pie chart