PSAT Math Grid-Ins Question 74: Answer and Explanation
Question: 74
The following table shows the chemical makeup of one mole (a unit of measure commonly used in chemistry) of acetone and the approximate mass of a mole of each component element.
| Chemical Makeup of One Mole of Acetone | ||
|---|---|---|
| Element | Number of Moles | Mass per Mole (grams) |
| Oxygen | 1 | 16 |
| Carbon | 3 | 12 |
| Hydrogen | 6 | 1 |
Oxygen makes up what percent of the mass of 1 mole of acetone? Round your answer to the nearest whole percent
Correct Answer: 28
Explanation:
28
Difficulty: Medium
Getting to the Answer: Use the formula:
To use the formula, find the part of the mass represented by oxygen: there is 1 mole of oxygen and it has a mass of 16 grams. Next, find the whole mass of 1 mole of acetone: 1 mole oxygen (16 g) + 3 moles carbon (3 × 12 = 36 g) + 6 moles hydrogen (6 × 1 = 6 g) = 16 + 36 + 6 = 58. Now, use the percent formula:
Before you grid in your answer, make sure you follow the directions—round to the nearest whole percent. Grid in 28.
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