What is the mass of oxygen atoms in 0.250 mol of sulfuric acid, H2SO4? (Molar masses: H = 1.0 g/mol, S = 32.1 g/mol, O = 16.0 g/mol)
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Correct answer
B. 16.0 g
Principle or equation
The amount of a substance in moles can be converted to mass using the molar mass. For a compound, the mass of a particular element is found by multiplying the number of moles of that element (from the formula) by its molar mass.
Why this answer is correct
In one mole of H2SO4, there are 4 moles of oxygen atoms. Therefore, 0.250 mol of H2SO4 contains 0.250 × 4 = 1.00 mol of oxygen atoms. The mass of oxygen is 1.00 mol × 16.0 g/mol = 16.0 g.
Example
For 0.500 mol of CO2, the mass of oxygen atoms is 0.500 × 2 × 16.0 g = 16.0 g.
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