mass fractions of calcium phosphide

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calcium phosphide | elemental composition

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$Find the elemental composition for calcium phosphide 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: Ca_3P_2 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 Ca (calcium) | 3 P (phosphorus) | 2 N_atoms = 3 + 2 = 5 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 Ca (calcium) | 3 | 3/5 P (phosphorus) | 2 | 2/5 Check: 3/5 + 2/5 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent Ca (calcium) | 3 | 3/5 × 100% = 60.0% P (phosphorus) | 2 | 2/5 × 100% = 40.0% 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 Ca (calcium) | 3 | 60.0% | 40.078 P (phosphorus) | 2 | 40.0% | 30.973761998 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 Ca (calcium) | 3 | 60.0% | 40.078 | 3 × 40.078 = 120.234 P (phosphorus) | 2 | 40.0% | 30.973761998 | 2 × 30.973761998 = 61.947523996 m = 120.234 u + 61.947523996 u = 182.181523996 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 Ca (calcium) | 3 | 60.0% | 120.234/182.181523996 P (phosphorus) | 2 | 40.0% | 61.947523996/182.181523996 Check: 120.234/182.181523996 + 61.947523996/182.181523996 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent Ca (calcium) | 3 | 60.0% | 120.234/182.181523996 × 100% = 66.00% P (phosphorus) | 2 | 40.0% | 61.947523996/182.181523996 × 100% = 34.00%$

Find the elemental composition for calcium phosphide 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: Ca_3P_2 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 Ca (calcium) | 3 P (phosphorus) | 2 N_atoms = 3 + 2 = 5 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 Ca (calcium) | 3 | 3/5 P (phosphorus) | 2 | 2/5 Check: 3/5 + 2/5 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent Ca (calcium) | 3 | 3/5 × 100% = 60.0% P (phosphorus) | 2 | 2/5 × 100% = 40.0% 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 Ca (calcium) | 3 | 60.0% | 40.078 P (phosphorus) | 2 | 40.0% | 30.973761998 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 Ca (calcium) | 3 | 60.0% | 40.078 | 3 × 40.078 = 120.234 P (phosphorus) | 2 | 40.0% | 30.973761998 | 2 × 30.973761998 = 61.947523996 m = 120.234 u + 61.947523996 u = 182.181523996 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 Ca (calcium) | 3 | 60.0% | 120.234/182.181523996 P (phosphorus) | 2 | 40.0% | 61.947523996/182.181523996 Check: 120.234/182.181523996 + 61.947523996/182.181523996 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent Ca (calcium) | 3 | 60.0% | 120.234/182.181523996 × 100% = 66.00% P (phosphorus) | 2 | 40.0% | 61.947523996/182.181523996 × 100% = 34.00%