mass fractions of 5,6,11,12-tetraphenylnaphthacene

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5, 6, 11, 12-tetraphenylnaphthacene | elemental composition

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$Find the elemental composition for 5, 6, 11, 12-tetraphenylnaphthacene 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: C_42H_28 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 C (carbon) | 42 H (hydrogen) | 28 N_atoms = 42 + 28 = 70 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 C (carbon) | 42 | 42/70 H (hydrogen) | 28 | 28/70 Check: 42/70 + 28/70 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 42 | 42/70 × 100% = 60.0% H (hydrogen) | 28 | 28/70 × 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 C (carbon) | 42 | 60.0% | 12.011 H (hydrogen) | 28 | 40.0% | 1.008 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 C (carbon) | 42 | 60.0% | 12.011 | 42 × 12.011 = 504.462 H (hydrogen) | 28 | 40.0% | 1.008 | 28 × 1.008 = 28.224 m = 504.462 u + 28.224 u = 532.686 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 C (carbon) | 42 | 60.0% | 504.462/532.686 H (hydrogen) | 28 | 40.0% | 28.224/532.686 Check: 504.462/532.686 + 28.224/532.686 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 42 | 60.0% | 504.462/532.686 × 100% = 94.70% H (hydrogen) | 28 | 40.0% | 28.224/532.686 × 100% = 5.298%$

Find the elemental composition for 5, 6, 11, 12-tetraphenylnaphthacene 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: C_42H_28 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 C (carbon) | 42 H (hydrogen) | 28 N_atoms = 42 + 28 = 70 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 C (carbon) | 42 | 42/70 H (hydrogen) | 28 | 28/70 Check: 42/70 + 28/70 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 42 | 42/70 × 100% = 60.0% H (hydrogen) | 28 | 28/70 × 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 C (carbon) | 42 | 60.0% | 12.011 H (hydrogen) | 28 | 40.0% | 1.008 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 C (carbon) | 42 | 60.0% | 12.011 | 42 × 12.011 = 504.462 H (hydrogen) | 28 | 40.0% | 1.008 | 28 × 1.008 = 28.224 m = 504.462 u + 28.224 u = 532.686 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 C (carbon) | 42 | 60.0% | 504.462/532.686 H (hydrogen) | 28 | 40.0% | 28.224/532.686 Check: 504.462/532.686 + 28.224/532.686 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 42 | 60.0% | 504.462/532.686 × 100% = 94.70% H (hydrogen) | 28 | 40.0% | 28.224/532.686 × 100% = 5.298%