Multiple Choice
What is the mass percent of sodium (Na) in a formula unit of sodium hydrogen carbonate (NaHCO_3)?
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3. Chemical Reactions
Mass Percent
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What is the mass percent of oxygen in aluminum oxide (Al_2O_3)?
A
53.0%
B
47.1%
C
60.0%
D
35.0%
Verified step by step guidance1
Identify the chemical formula of aluminum oxide, which is \(\mathrm{Al_2O_3}\), meaning it contains 2 aluminum atoms and 3 oxygen atoms per formula unit.
Find the atomic masses of aluminum (Al) and oxygen (O) from the periodic table. Aluminum has an atomic mass of approximately 26.98 g/mol, and oxygen has an atomic mass of approximately 16.00 g/mol.
Calculate the molar mass of aluminum oxide by summing the masses of all atoms in the formula: \(\mathrm{Molar\ mass} = 2 \times 26.98 + 3 \times 16.00\) g/mol.
Calculate the total mass of oxygen in one mole of aluminum oxide: \(\mathrm{Mass\ of\ oxygen} = 3 \times 16.00\) g.
Determine the mass percent of oxygen by dividing the total mass of oxygen by the molar mass of aluminum oxide and multiplying by 100: \(\mathrm{Mass\ \%\ of\ oxygen} = \left( \frac{3 \times 16.00}{\mathrm{Molar\ mass}} \right) \times 100\).
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