mass fractions of 4-methyl-5-thiazoleethanol

4-methyl-5-thiazoleethanol | elemental composition

Find the elemental composition for 4-methyl-5-thiazoleethanol 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_6H_9NOS 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) | 6 H (hydrogen) | 9 N (nitrogen) | 1 O (oxygen) | 1 S (sulfur) | 1 N_atoms = 6 + 9 + 1 + 1 + 1 = 18 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) | 6 | 6/18 H (hydrogen) | 9 | 9/18 N (nitrogen) | 1 | 1/18 O (oxygen) | 1 | 1/18 S (sulfur) | 1 | 1/18 Check: 6/18 + 9/18 + 1/18 + 1/18 + 1/18 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 6 | 6/18 × 100% = 33.3% H (hydrogen) | 9 | 9/18 × 100% = 50.0% N (nitrogen) | 1 | 1/18 × 100% = 5.56% O (oxygen) | 1 | 1/18 × 100% = 5.56% S (sulfur) | 1 | 1/18 × 100% = 5.56% 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) | 6 | 33.3% | 12.011 H (hydrogen) | 9 | 50.0% | 1.008 N (nitrogen) | 1 | 5.56% | 14.007 O (oxygen) | 1 | 5.56% | 15.999 S (sulfur) | 1 | 5.56% | 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) | 6 | 33.3% | 12.011 | 6 × 12.011 = 72.066 H (hydrogen) | 9 | 50.0% | 1.008 | 9 × 1.008 = 9.072 N (nitrogen) | 1 | 5.56% | 14.007 | 1 × 14.007 = 14.007 O (oxygen) | 1 | 5.56% | 15.999 | 1 × 15.999 = 15.999 S (sulfur) | 1 | 5.56% | 32.06 | 1 × 32.06 = 32.06 m = 72.066 u + 9.072 u + 14.007 u + 15.999 u + 32.06 u = 143.204 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) | 6 | 33.3% | 72.066/143.204 H (hydrogen) | 9 | 50.0% | 9.072/143.204 N (nitrogen) | 1 | 5.56% | 14.007/143.204 O (oxygen) | 1 | 5.56% | 15.999/143.204 S (sulfur) | 1 | 5.56% | 32.06/143.204 Check: 72.066/143.204 + 9.072/143.204 + 14.007/143.204 + 15.999/143.204 + 32.06/143.204 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 6 | 33.3% | 72.066/143.204 × 100% = 50.32% H (hydrogen) | 9 | 50.0% | 9.072/143.204 × 100% = 6.335% N (nitrogen) | 1 | 5.56% | 14.007/143.204 × 100% = 9.781% O (oxygen) | 1 | 5.56% | 15.999/143.204 × 100% = 11.17% S (sulfur) | 1 | 5.56% | 32.06/143.204 × 100% = 22.39%

Mass fraction pie chart