Question

Express the composition of each of the following compounds as the mass percents of its elements. a. formaldehyde, \(\mathrm{CH}_{2} \mathrm{O}\) b. glucose, \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\) c. acetic acid, \(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\)

Short answer

a. Formaldehyde, \(\mathrm{CH}_{2} \mathrm{O}\): - Carbon: \(40.0\%\) - Hydrogen: \(6.7\%\) - Oxygen: \(53.3\%\) b. Glucose, \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\): - Carbon: \(40.0\%\) - Hydrogen: \(6.7\%\) - Oxygen: \(53.3\%\) c. Acetic acid, \(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\): - Hydrogen: \(4.1\%\) - Carbon: \(39.9\%\) - Oxygen: \(56.0\%\)

Step-by-step solution

Calculate the molar mass of the compounds

Calculate the molar mass of each compound by adding the molar masses of their individual constituent elements. For example, the molar mass of formaldehyde (\(\mathrm{CH}_{2} \mathrm{O}\)): - Carbon: \(1 \times 12.01 \, \mathrm{g/mol} = 12.01 \, \mathrm{g/mol}\) - Hydrogen: \(2 \times 1.01 \, \mathrm{g/mol} = 2.02 \, \mathrm{g/mol}\) - Oxygen: \(1 \times 16.00 \, \mathrm{g/mol} = 16.00 \, \mathrm{g/mol}\) Apply the same calculation for glucose (\(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\)) and acetic acid (\(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\)).

Calculate the mass percent of each element

To find the mass percent of each element, divide the total mass of the element in the compound by the total molar mass of the compound, then multiply by 100. For example, the mass percent of the elements in formaldehyde: - Carbon: \(\dfrac{12.01 \, \mathrm{g/mol}}{12.01+2.02+16.00 \, \mathrm{g/mol}} \times 100\% = 40.0\%\) - Hydrogen: \(\dfrac{2.02 \, \mathrm{g/mol}}{12.01+2.02+16.00 \, \mathrm{g/mol}} \times 100\% = 6.7\%\) - Oxygen: \(\dfrac{16.00 \, \mathrm{g/mol}}{12.01+2.02+16.00 \, \mathrm{g/mol}} \times 100\% = 53.3\%\) Apply the same calculation for each element in glucose (\(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\)) and acetic acid (\(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\)).

Final Answer

a. Formaldehyde, \(\mathrm{CH}_{2} \mathrm{O}\): - Carbon: \(40.0\%\) - Hydrogen: \(6.7\%\) - Oxygen: \(53.3\%\) b. Glucose, \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\): - Calculate the mass percent for carbon, hydrogen, and oxygen in glucose following steps 1 and 2. c. Acetic acid, \(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\): - Calculate the mass percent for hydrogen, carbon, and oxygen in acetic acid following steps 1 and 2.