element mass fraction of indium(III) nitrate trihydrate

indium(III) nitrate trihydrate | elemental composition

Find the elemental composition for indium(III) nitrate trihydrate 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: In(NO)_3·3H_2O 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 H (hydrogen) | 6 In (indium) | 1 N (nitrogen) | 3 O (oxygen) | 12 N_atoms = 6 + 1 + 3 + 12 = 22 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 H (hydrogen) | 6 | 6/22 In (indium) | 1 | 1/22 N (nitrogen) | 3 | 3/22 O (oxygen) | 12 | 12/22 Check: 6/22 + 1/22 + 3/22 + 12/22 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent H (hydrogen) | 6 | 6/22 × 100% = 27.3% In (indium) | 1 | 1/22 × 100% = 4.55% N (nitrogen) | 3 | 3/22 × 100% = 13.6% O (oxygen) | 12 | 12/22 × 100% = 54.5% 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 H (hydrogen) | 6 | 27.3% | 1.008 In (indium) | 1 | 4.55% | 114.818 N (nitrogen) | 3 | 13.6% | 14.007 O (oxygen) | 12 | 54.5% | 15.999 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 H (hydrogen) | 6 | 27.3% | 1.008 | 6 × 1.008 = 6.048 In (indium) | 1 | 4.55% | 114.818 | 1 × 114.818 = 114.818 N (nitrogen) | 3 | 13.6% | 14.007 | 3 × 14.007 = 42.021 O (oxygen) | 12 | 54.5% | 15.999 | 12 × 15.999 = 191.988 m = 6.048 u + 114.818 u + 42.021 u + 191.988 u = 354.875 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 H (hydrogen) | 6 | 27.3% | 6.048/354.875 In (indium) | 1 | 4.55% | 114.818/354.875 N (nitrogen) | 3 | 13.6% | 42.021/354.875 O (oxygen) | 12 | 54.5% | 191.988/354.875 Check: 6.048/354.875 + 114.818/354.875 + 42.021/354.875 + 191.988/354.875 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent H (hydrogen) | 6 | 27.3% | 6.048/354.875 × 100% = 1.704% In (indium) | 1 | 4.55% | 114.818/354.875 × 100% = 32.35% N (nitrogen) | 3 | 13.6% | 42.021/354.875 × 100% = 11.84% O (oxygen) | 12 | 54.5% | 191.988/354.875 × 100% = 54.10%

Mass fraction pie chart