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How many grams of NaNO3 are required to prepare 50 mL of an aqueous solution that contains 70.0 mg of Na+ per mL of solution? (Round to the nearest integer.) [Atomic masses in g/mol: Na = 23, N = 14, O = 16]

1. 13 g
2. 26 g
3. 9 g
4. 18 g

Correct answer: 13 g

Solution

The total Na+ mass (3.5 g) gives the moles of Na, which equals moles of NaNO3; multiplying by 85 g/mol gives about 13 g.

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