10. when a 13.6 g sample of a compound containing only magnesium and oxygen is decomposed, 5.4 g of oxygen is obtained. what is the percent of
magnesium in this sample?
• 5.4 g / 13.6 g * 100
• (13.6 g- 5.4g) / 13.6 g x 100
• (13.6 g- 5.4g) x 100
• 5.4g/ (13.6 g-5.4g) x 100

• (13.6 g- 5.4g) / 13.6 g x 100 is the correct option

Explanation:

Total mass of the sample containing only magnesium and oxygen is 13.6 grams. This means that the sum of the mass of oxygen and the mass of magnesium is 13.6 grams.

On decomposition of the sample, 5.4 g of oxygen is obtained. This means that the mass of magnesium that was obtained would be

13.6 - 5.4 = 8.2 grams of magnesium. Therefore, the percentage of magnesium in this sample would be

8.2/13.6 × 100 = 60.294%