mass fractions of silver telluride

silver telluride | elemental composition

Find the elemental composition for silver telluride 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: Ag_2Te 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 Ag (silver) | 2 Te (tellurium) | 1 N_atoms = 2 + 1 = 3 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 Ag (silver) | 2 | 2/3 Te (tellurium) | 1 | 1/3 Check: 2/3 + 1/3 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent Ag (silver) | 2 | 2/3 × 100% = 66.7% Te (tellurium) | 1 | 1/3 × 100% = 33.3% 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 Ag (silver) | 2 | 66.7% | 107.8682 Te (tellurium) | 1 | 33.3% | 127.60 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 Ag (silver) | 2 | 66.7% | 107.8682 | 2 × 107.8682 = 215.7364 Te (tellurium) | 1 | 33.3% | 127.60 | 1 × 127.60 = 127.60 m = 215.7364 u + 127.60 u = 343.3364 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 Ag (silver) | 2 | 66.7% | 215.7364/343.3364 Te (tellurium) | 1 | 33.3% | 127.60/343.3364 Check: 215.7364/343.3364 + 127.60/343.3364 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent Ag (silver) | 2 | 66.7% | 215.7364/343.3364 × 100% = 62.84% Te (tellurium) | 1 | 33.3% | 127.60/343.3364 × 100% = 37.16%

Mass fraction pie chart