A water sample has a mass of 25.0 g. It contains 1.56 × 10–5 g NaCl. What is the best set up to find ppm?

For a mass-based concentration, ppm is calculated as (mass of solute ÷ mass of solution) × 10⁶. Here, the setup is (1.56 × 10⁻⁵ g NaCl ÷ 25.0 g solution) × 10⁶. Therefore, the correct choice is “mass solute/mass solution × 10⁶.”

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