mass fractions of sodium stannate

sodium stannate | elemental composition

Find the elemental composition for sodium stannate 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: Na_2SnO_3 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 Na (sodium) | 2 O (oxygen) | 3 Sn (tin) | 1 N_atoms = 2 + 3 + 1 = 6 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 Na (sodium) | 2 | 2/6 O (oxygen) | 3 | 3/6 Sn (tin) | 1 | 1/6 Check: 2/6 + 3/6 + 1/6 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent Na (sodium) | 2 | 2/6 × 100% = 33.3% O (oxygen) | 3 | 3/6 × 100% = 50.0% Sn (tin) | 1 | 1/6 × 100% = 16.7% 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 Na (sodium) | 2 | 33.3% | 22.98976928 O (oxygen) | 3 | 50.0% | 15.999 Sn (tin) | 1 | 16.7% | 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 Na (sodium) | 2 | 33.3% | 22.98976928 | 2 × 22.98976928 = 45.97953856 O (oxygen) | 3 | 50.0% | 15.999 | 3 × 15.999 = 47.997 Sn (tin) | 1 | 16.7% | 118.710 | 1 × 118.710 = 118.710 m = 45.97953856 u + 47.997 u + 118.710 u = 212.68653856 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 Na (sodium) | 2 | 33.3% | 45.97953856/212.68653856 O (oxygen) | 3 | 50.0% | 47.997/212.68653856 Sn (tin) | 1 | 16.7% | 118.710/212.68653856 Check: 45.97953856/212.68653856 + 47.997/212.68653856 + 118.710/212.68653856 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent Na (sodium) | 2 | 33.3% | 45.97953856/212.68653856 × 100% = 21.62% O (oxygen) | 3 | 50.0% | 47.997/212.68653856 × 100% = 22.57% Sn (tin) | 1 | 16.7% | 118.710/212.68653856 × 100% = 55.81%

Mass fraction pie chart