A sample of water has a mass of 10.0 grams. What is the number of molecules of water in the sample? (H = 1 u, O = 16 u, and 1 u = 1.66 × 10⁻²⁷ kg.) A) 1.99 × 10²³ B) 2.00 × 10²³ C) 2.56 × 10²³ D) 3.35 × 10²³ E) 4.25 × 10²³

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Quizplus · Accepted Answer

The molar mass of water (H₂O) is 18 g/mol. Therefore, 10.0 grams of water is 10.0/18 moles. Using Avogadro's number (6.022 × 10²³ molecules/mol), the number of molecules is (10.0/18) × 6.022 × 10²³ ≈ 3.35 × 10²³ molecules.

A Sample of Water Has a Mass of 10