mass fractions of tin(II) pyrophosphate

tin(II) pyrophosphate | elemental composition

Find the elemental composition for tin(II) pyrophosphate 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: Sn_2P_2O_7 Use the chemical formula, Sn_2P_2O_7, to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms: | number of atoms O (oxygen) | 7 P (phosphorus) | 2 Sn (tin) | 2 N_atoms = 7 + 2 + 2 = 11 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 O (oxygen) | 7 | 7/11 P (phosphorus) | 2 | 2/11 Sn (tin) | 2 | 2/11 Check: 7/11 + 2/11 + 2/11 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent O (oxygen) | 7 | 7/11 × 100% = 63.6% P (phosphorus) | 2 | 2/11 × 100% = 18.2% Sn (tin) | 2 | 2/11 × 100% = 18.2% 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 O (oxygen) | 7 | 63.6% | 15.999 P (phosphorus) | 2 | 18.2% | 30.973761998 Sn (tin) | 2 | 18.2% | 118.710 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 O (oxygen) | 7 | 63.6% | 15.999 | 7 × 15.999 = 111.993 P (phosphorus) | 2 | 18.2% | 30.973761998 | 2 × 30.973761998 = 61.947523996 Sn (tin) | 2 | 18.2% | 118.710 | 2 × 118.710 = 237.420 m = 111.993 u + 61.947523996 u + 237.420 u = 411.360523996 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 O (oxygen) | 7 | 63.6% | 111.993/411.360523996 P (phosphorus) | 2 | 18.2% | 61.947523996/411.360523996 Sn (tin) | 2 | 18.2% | 237.420/411.360523996 Check: 111.993/411.360523996 + 61.947523996/411.360523996 + 237.420/411.360523996 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent O (oxygen) | 7 | 63.6% | 111.993/411.360523996 × 100% = 27.23% P (phosphorus) | 2 | 18.2% | 61.947523996/411.360523996 × 100% = 15.06% Sn (tin) | 2 | 18.2% | 237.420/411.360523996 × 100% = 57.72%

Mass fraction pie chart