What is the mass of 0.250 mol of sodium carbonate (Na2CO3)? (Molar masses: Na = 23.0 g/mol, C = 12.0 g/mol, O = 16.0 g/mol)
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Correct answer
C. 26.5 g
Principle or equation
Mass = amount of substance (mol) × molar mass (g/mol).
Why this answer is correct
Molar mass of Na2CO3 = 2(23.0) + 12.0 + 3(16.0) = 46.0 + 12.0 + 48.0 = 106.0 g/mol. Mass = 0.250 mol × 106.0 g/mol = 26.5 g.
Example
For 0.500 mol of CaCO3 (molar mass 100 g/mol), mass = 0.500 × 100 = 50.0 g.
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