mass fractions of hydrazoic acid

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hydrazoic acid | elemental composition

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$Find the elemental composition for hydrazoic acid 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: HNN congruent N 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 H (hydrogen) | 1 N (nitrogen) | 3 N_atoms = 1 + 3 = 4 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 H (hydrogen) | 1 | 1/4 N (nitrogen) | 3 | 3/4 Check: 1/4 + 3/4 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent H (hydrogen) | 1 | 1/4 × 100% = 25.0% N (nitrogen) | 3 | 3/4 × 100% = 75.0% 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 H (hydrogen) | 1 | 25.0% | 1.008 N (nitrogen) | 3 | 75.0% | 14.007 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 H (hydrogen) | 1 | 25.0% | 1.008 | 1 × 1.008 = 1.008 N (nitrogen) | 3 | 75.0% | 14.007 | 3 × 14.007 = 42.021 m = 1.008 u + 42.021 u = 43.029 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 H (hydrogen) | 1 | 25.0% | 1.008/43.029 N (nitrogen) | 3 | 75.0% | 42.021/43.029 Check: 1.008/43.029 + 42.021/43.029 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent H (hydrogen) | 1 | 25.0% | 1.008/43.029 × 100% = 2.343% N (nitrogen) | 3 | 75.0% | 42.021/43.029 × 100% = 97.66%$

Find the elemental composition for hydrazoic acid 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: HNN congruent N 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 H (hydrogen) | 1 N (nitrogen) | 3 N_atoms = 1 + 3 = 4 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 H (hydrogen) | 1 | 1/4 N (nitrogen) | 3 | 3/4 Check: 1/4 + 3/4 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent H (hydrogen) | 1 | 1/4 × 100% = 25.0% N (nitrogen) | 3 | 3/4 × 100% = 75.0% 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 H (hydrogen) | 1 | 25.0% | 1.008 N (nitrogen) | 3 | 75.0% | 14.007 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 H (hydrogen) | 1 | 25.0% | 1.008 | 1 × 1.008 = 1.008 N (nitrogen) | 3 | 75.0% | 14.007 | 3 × 14.007 = 42.021 m = 1.008 u + 42.021 u = 43.029 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 H (hydrogen) | 1 | 25.0% | 1.008/43.029 N (nitrogen) | 3 | 75.0% | 42.021/43.029 Check: 1.008/43.029 + 42.021/43.029 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent H (hydrogen) | 1 | 25.0% | 1.008/43.029 × 100% = 2.343% N (nitrogen) | 3 | 75.0% | 42.021/43.029 × 100% = 97.66%