Question

A 25.0-gram sample of magnesium oxide contains 10.8 grams of magnesium. What is the
percent of oxygen by mass in this compound?
(2 points)
a. 89.2 %
C. 43.2%
b. 14.2 %
d. 56.8 %

Answer 1

Answer: b. 14.2%

Explanation: I'm not sure if it's correct but I did it this way. Since we have a 25.0 gram of magnesium oxide by the name of it we should know that the 25.0 gram is composed of magnesium and oxygen. It tells us that we have 10.8 grams of magnesium. Therefore we can subtract 25.0- 10.8 = 14.2 so our answer would be 14.2% of oxygen.