mass fractions of chlorosyl trifluoride

chlorosyl trifluoride | elemental composition

Find the elemental composition for chlorosyl trifluoride 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: ClOF_3 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 Cl (chlorine) | 1 F (fluorine) | 3 O (oxygen) | 1 N_atoms = 1 + 3 + 1 = 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 Cl (chlorine) | 1 | 1/5 F (fluorine) | 3 | 3/5 O (oxygen) | 1 | 1/5 Check: 1/5 + 3/5 + 1/5 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent Cl (chlorine) | 1 | 1/5 × 100% = 20.0% F (fluorine) | 3 | 3/5 × 100% = 60.0% O (oxygen) | 1 | 1/5 × 100% = 20.0% 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 Cl (chlorine) | 1 | 20.0% | 35.45 F (fluorine) | 3 | 60.0% | 18.998403163 O (oxygen) | 1 | 20.0% | 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 Cl (chlorine) | 1 | 20.0% | 35.45 | 1 × 35.45 = 35.45 F (fluorine) | 3 | 60.0% | 18.998403163 | 3 × 18.998403163 = 56.995209489 O (oxygen) | 1 | 20.0% | 15.999 | 1 × 15.999 = 15.999 m = 35.45 u + 56.995209489 u + 15.999 u = 108.444209489 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 Cl (chlorine) | 1 | 20.0% | 35.45/108.444209489 F (fluorine) | 3 | 60.0% | 56.995209489/108.444209489 O (oxygen) | 1 | 20.0% | 15.999/108.444209489 Check: 35.45/108.444209489 + 56.995209489/108.444209489 + 15.999/108.444209489 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent Cl (chlorine) | 1 | 20.0% | 35.45/108.444209489 × 100% = 32.69% F (fluorine) | 3 | 60.0% | 56.995209489/108.444209489 × 100% = 52.56% O (oxygen) | 1 | 20.0% | 15.999/108.444209489 × 100% = 14.75%

Mass fraction pie chart