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A 55 g serving of cereal supplies 270 mg of sodium, which is 11% of the recommended daily allowance. How many moles of sodium are in the full daily allowance? Use Na = 22.99 g/mol.
A0.0117 mol
B1.07 mol
C0.214 mol
D0.107 mol
Answer & Solution
Correct answer: D. 0.107 mol
1. First scale up to the full allowance: 270 mg is 11 percent of it.
2. The full allowance is 270 mg / 0.11 = 2455 mg of sodium.
3. Convert to grams: 2455 mg = 2.455 g of sodium.
4. Convert to moles: 2.455 g / 22.99 g/mol = 0.107 mol of sodium.
5. Units check: milligrams become grams in step 3 and grams cancel against grams per mole in step 4.
6. The value 0.0117 mol skips the 11 percent scaling and converts the single serving instead.
7. The value 1.07 mol is a one decimal place slip, and 0.214 mol doubles the answer.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 3 "Composition of Substances and Solutions", section 3.1 Formula Mass and the Mole Concept_
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