mass fractions of tungsten(VI) fluoride

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tungsten(VI) fluoride | elemental composition

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$Find the elemental composition for tungsten(VI) fluoride 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: WF_6 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 F (fluorine) | 6 W (tungsten) | 1 N_atoms = 6 + 1 = 7 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 F (fluorine) | 6 | 6/7 W (tungsten) | 1 | 1/7 Check: 6/7 + 1/7 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent F (fluorine) | 6 | 6/7 × 100% = 85.7% W (tungsten) | 1 | 1/7 × 100% = 14.3% 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 F (fluorine) | 6 | 85.7% | 18.998403163 W (tungsten) | 1 | 14.3% | 183.84 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 F (fluorine) | 6 | 85.7% | 18.998403163 | 6 × 18.998403163 = 113.990418978 W (tungsten) | 1 | 14.3% | 183.84 | 1 × 183.84 = 183.84 m = 113.990418978 u + 183.84 u = 297.830418978 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 F (fluorine) | 6 | 85.7% | 113.990418978/297.830418978 W (tungsten) | 1 | 14.3% | 183.84/297.830418978 Check: 113.990418978/297.830418978 + 183.84/297.830418978 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent F (fluorine) | 6 | 85.7% | 113.990418978/297.830418978 × 100% = 38.27% W (tungsten) | 1 | 14.3% | 183.84/297.830418978 × 100% = 61.73%$

Find the elemental composition for tungsten(VI) fluoride 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: WF_6 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 F (fluorine) | 6 W (tungsten) | 1 N_atoms = 6 + 1 = 7 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 F (fluorine) | 6 | 6/7 W (tungsten) | 1 | 1/7 Check: 6/7 + 1/7 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent F (fluorine) | 6 | 6/7 × 100% = 85.7% W (tungsten) | 1 | 1/7 × 100% = 14.3% 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 F (fluorine) | 6 | 85.7% | 18.998403163 W (tungsten) | 1 | 14.3% | 183.84 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 F (fluorine) | 6 | 85.7% | 18.998403163 | 6 × 18.998403163 = 113.990418978 W (tungsten) | 1 | 14.3% | 183.84 | 1 × 183.84 = 183.84 m = 113.990418978 u + 183.84 u = 297.830418978 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 F (fluorine) | 6 | 85.7% | 113.990418978/297.830418978 W (tungsten) | 1 | 14.3% | 183.84/297.830418978 Check: 113.990418978/297.830418978 + 183.84/297.830418978 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent F (fluorine) | 6 | 85.7% | 113.990418978/297.830418978 × 100% = 38.27% W (tungsten) | 1 | 14.3% | 183.84/297.830418978 × 100% = 61.73%