mass fractions of glycoprotein-phospho-D-mannose

glycoprotein-phospho-D-mannose | elemental composition

Find the elemental composition for glycoprotein-phospho-D-mannose 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_34H_58N_5O_26P_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) | 34 H (hydrogen) | 56 N (nitrogen) | 5 O (oxygen) | 26 P (phosphorus) | 1 N_atoms = 34 + 56 + 5 + 26 + 1 = 122 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) | 34 | 34/122 H (hydrogen) | 56 | 56/122 N (nitrogen) | 5 | 5/122 O (oxygen) | 26 | 26/122 P (phosphorus) | 1 | 1/122 Check: 34/122 + 56/122 + 5/122 + 26/122 + 1/122 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 34 | 34/122 × 100% = 27.9% H (hydrogen) | 56 | 56/122 × 100% = 45.9% N (nitrogen) | 5 | 5/122 × 100% = 4.10% O (oxygen) | 26 | 26/122 × 100% = 21.3% P (phosphorus) | 1 | 1/122 × 100% = 0.820% 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) | 34 | 27.9% | 12.011 H (hydrogen) | 56 | 45.9% | 1.008 N (nitrogen) | 5 | 4.10% | 14.007 O (oxygen) | 26 | 21.3% | 15.999 P (phosphorus) | 1 | 0.820% | 30.973761998 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) | 34 | 27.9% | 12.011 | 34 × 12.011 = 408.374 H (hydrogen) | 56 | 45.9% | 1.008 | 56 × 1.008 = 56.448 N (nitrogen) | 5 | 4.10% | 14.007 | 5 × 14.007 = 70.035 O (oxygen) | 26 | 21.3% | 15.999 | 26 × 15.999 = 415.974 P (phosphorus) | 1 | 0.820% | 30.973761998 | 1 × 30.973761998 = 30.973761998 m = 408.374 u + 56.448 u + 70.035 u + 415.974 u + 30.973761998 u = 981.804761998 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) | 34 | 27.9% | 408.374/981.804761998 H (hydrogen) | 56 | 45.9% | 56.448/981.804761998 N (nitrogen) | 5 | 4.10% | 70.035/981.804761998 O (oxygen) | 26 | 21.3% | 415.974/981.804761998 P (phosphorus) | 1 | 0.820% | 30.973761998/981.804761998 Check: 408.374/981.804761998 + 56.448/981.804761998 + 70.035/981.804761998 + 415.974/981.804761998 + 30.973761998/981.804761998 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 34 | 27.9% | 408.374/981.804761998 × 100% = 41.59% H (hydrogen) | 56 | 45.9% | 56.448/981.804761998 × 100% = 5.749% N (nitrogen) | 5 | 4.10% | 70.035/981.804761998 × 100% = 7.133% O (oxygen) | 26 | 21.3% | 415.974/981.804761998 × 100% = 42.37% P (phosphorus) | 1 | 0.820% | 30.973761998/981.804761998 × 100% = 3.155%

Mass fraction pie chart