In a laboratory preparation, a student obtained 18.5 g of magnesium oxide from burning magnesium ribbon. The theoretical yield was 20.0 g. The student then discovered that the product contained 1.5 g of unreacted magnesium. What is the percentage purity of the magnesium oxide produced?

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Question

In a laboratory preparation, a student obtained 18.5 g of magnesium oxide from burning magnesium ribbon. The theoretical yield was 20.0 g. The student then discovered that the product contained 1.5 g of unreacted magnesium. What is the percentage purity of the magnesium oxide produced?

Accepted Answer

91.9% — 9%. Award 1 mark for correct calculation: mass of pure MgO = 18.5 - 1.5 = 17.0 g; percentage purity = (17.0/18.5) × 100 = 91.9%. B is incorrect — this uses theoretical yield as denominator. C is incorrect — this represents percentage impurity. D is incorrect — this results from an incorrect calculation method.

Answer

8.1%

Answer

75.0%

Answer

91.9%

Answer

92.5%

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