mass fractions of calcium telluride

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calcium telluride | elemental composition

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$Find the elemental composition for calcium telluride 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: CaTe 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) | 1 Te (tellurium) | 1 N_atoms = 1 + 1 = 2 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) | 1 | 1/2 Te (tellurium) | 1 | 1/2 Check: 1/2 + 1/2 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent Ca (calcium) | 1 | 1/2 × 100% = 50.0% Te (tellurium) | 1 | 1/2 × 100% = 50.0% 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) | 1 | 50.0% | 40.078 Te (tellurium) | 1 | 50.0% | 127.60 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) | 1 | 50.0% | 40.078 | 1 × 40.078 = 40.078 Te (tellurium) | 1 | 50.0% | 127.60 | 1 × 127.60 = 127.60 m = 40.078 u + 127.60 u = 167.678 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) | 1 | 50.0% | 40.078/167.678 Te (tellurium) | 1 | 50.0% | 127.60/167.678 Check: 40.078/167.678 + 127.60/167.678 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent Ca (calcium) | 1 | 50.0% | 40.078/167.678 × 100% = 23.90% Te (tellurium) | 1 | 50.0% | 127.60/167.678 × 100% = 76.10%$

Find the elemental composition for calcium telluride 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: CaTe 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) | 1 Te (tellurium) | 1 N_atoms = 1 + 1 = 2 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) | 1 | 1/2 Te (tellurium) | 1 | 1/2 Check: 1/2 + 1/2 = 1 Compute atom percents using the atom fractions: | number of atoms | atom percent Ca (calcium) | 1 | 1/2 × 100% = 50.0% Te (tellurium) | 1 | 1/2 × 100% = 50.0% 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) | 1 | 50.0% | 40.078 Te (tellurium) | 1 | 50.0% | 127.60 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) | 1 | 50.0% | 40.078 | 1 × 40.078 = 40.078 Te (tellurium) | 1 | 50.0% | 127.60 | 1 × 127.60 = 127.60 m = 40.078 u + 127.60 u = 167.678 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) | 1 | 50.0% | 40.078/167.678 Te (tellurium) | 1 | 50.0% | 127.60/167.678 Check: 40.078/167.678 + 127.60/167.678 = 1 Compute mass percents using the mass fractions: Answer: | | | number of atoms | atom percent | mass percent Ca (calcium) | 1 | 50.0% | 40.078/167.678 × 100% = 23.90% Te (tellurium) | 1 | 50.0% | 127.60/167.678 × 100% = 76.10%