A 42.7 gram sample of potassium nitrate contains how many grams of potassium?

Question

Quizplus · Accepted Answer

The formula for potassium nitrate is KNO3. The molar mass of KNO3 is 101.1 g/mol. Therefore, the number of moles of KNO3 in the sample is 42.7 g / 101.1 g/mol = 0.422 mol. Since the formula ratio between K and KNO3 is 1:1, the number of moles of K in the sample is also 0.422 mol. The molar mass of K is 39.1 g/mol, so the mass of K in the sample is 0.422 mol x 39.1 g/mol = 16.5 g. Therefore, the answer is B) 16.5.

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