mass fractions of zinc iodide

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zinc iodide | elemental composition

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$Find the elemental composition for zinc iodide 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: ZnI_2 Use the chemical formula, ZnI_2, to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms: | number of atoms I (iodine) | 2 Zn (zinc) | 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 I (iodine) | 2 | 2/3 Zn (zinc) | 1 | 1/3 Check: 2/3 + 1/3 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent I (iodine) | 2 | 2/3 × 100% = 66.7% Zn (zinc) | 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 I (iodine) | 2 | 66.7% | 126.90447 Zn (zinc) | 1 | 33.3% | 65.38 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 I (iodine) | 2 | 66.7% | 126.90447 | 2 × 126.90447 = 253.80894 Zn (zinc) | 1 | 33.3% | 65.38 | 1 × 65.38 = 65.38 m = 253.80894 u + 65.38 u = 319.18894 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 I (iodine) | 2 | 66.7% | 253.80894/319.18894 Zn (zinc) | 1 | 33.3% | 65.38/319.18894 Check: 253.80894/319.18894 + 65.38/319.18894 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent I (iodine) | 2 | 66.7% | 253.80894/319.18894 × 100% = 79.52% Zn (zinc) | 1 | 33.3% | 65.38/319.18894 × 100% = 20.48%$

Find the elemental composition for zinc iodide 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: ZnI_2 Use the chemical formula, ZnI_2, to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms: | number of atoms I (iodine) | 2 Zn (zinc) | 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 I (iodine) | 2 | 2/3 Zn (zinc) | 1 | 1/3 Check: 2/3 + 1/3 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent I (iodine) | 2 | 2/3 × 100% = 66.7% Zn (zinc) | 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 I (iodine) | 2 | 66.7% | 126.90447 Zn (zinc) | 1 | 33.3% | 65.38 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 I (iodine) | 2 | 66.7% | 126.90447 | 2 × 126.90447 = 253.80894 Zn (zinc) | 1 | 33.3% | 65.38 | 1 × 65.38 = 65.38 m = 253.80894 u + 65.38 u = 319.18894 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 I (iodine) | 2 | 66.7% | 253.80894/319.18894 Zn (zinc) | 1 | 33.3% | 65.38/319.18894 Check: 253.80894/319.18894 + 65.38/319.18894 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent I (iodine) | 2 | 66.7% | 253.80894/319.18894 × 100% = 79.52% Zn (zinc) | 1 | 33.3% | 65.38/319.18894 × 100% = 20.48%