mass fractions of N-butylcyclohexane

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N-butylcyclohexane | elemental composition

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$Find the elemental composition for N-butylcyclohexane 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: CH_3(CH_2)_3C_6H_11 Use the chemical formula, CH_3(CH_2)_3C_6H_11, to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms: | number of atoms C (carbon) | 10 H (hydrogen) | 20 N_atoms = 10 + 20 = 30 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) | 10 | 10/30 H (hydrogen) | 20 | 20/30 Check: 10/30 + 20/30 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 10 | 10/30 × 100% = 33.3% H (hydrogen) | 20 | 20/30 × 100% = 66.7% 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) | 10 | 33.3% | 12.011 H (hydrogen) | 20 | 66.7% | 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) | 10 | 33.3% | 12.011 | 10 × 12.011 = 120.110 H (hydrogen) | 20 | 66.7% | 1.008 | 20 × 1.008 = 20.160 m = 120.110 u + 20.160 u = 140.270 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) | 10 | 33.3% | 120.110/140.270 H (hydrogen) | 20 | 66.7% | 20.160/140.270 Check: 120.110/140.270 + 20.160/140.270 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 10 | 33.3% | 120.110/140.270 × 100% = 85.63% H (hydrogen) | 20 | 66.7% | 20.160/140.270 × 100% = 14.37%$

Find the elemental composition for N-butylcyclohexane 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: CH_3(CH_2)_3C_6H_11 Use the chemical formula, CH_3(CH_2)_3C_6H_11, to count the number of atoms, N_i, for each element and find the total number of atoms, N_atoms: | number of atoms C (carbon) | 10 H (hydrogen) | 20 N_atoms = 10 + 20 = 30 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) | 10 | 10/30 H (hydrogen) | 20 | 20/30 Check: 10/30 + 20/30 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent C (carbon) | 10 | 10/30 × 100% = 33.3% H (hydrogen) | 20 | 20/30 × 100% = 66.7% 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) | 10 | 33.3% | 12.011 H (hydrogen) | 20 | 66.7% | 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) | 10 | 33.3% | 12.011 | 10 × 12.011 = 120.110 H (hydrogen) | 20 | 66.7% | 1.008 | 20 × 1.008 = 20.160 m = 120.110 u + 20.160 u = 140.270 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) | 10 | 33.3% | 120.110/140.270 H (hydrogen) | 20 | 66.7% | 20.160/140.270 Check: 120.110/140.270 + 20.160/140.270 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent C (carbon) | 10 | 33.3% | 120.110/140.270 × 100% = 85.63% H (hydrogen) | 20 | 66.7% | 20.160/140.270 × 100% = 14.37%