Question

What is the percent by mass of carbon in acetone, C3H6O?

Select one:
a. 20.7%
b. 30.0%
c. 1.61%
d. 62.1%

Answer 1

The correct answer is B. 30.0%. Acetone, C3H6O, has three carbon atoms and six hydrogen atoms. The molar mass of C3H6O is 58.08 g/mol. The mass of carbon in one mole of C3H6O is 3 x 12.01 g = 36.03 g. Therefore, the percent by mass of carbon in C3H6O is 36.03/58.08 x 100 = 61.99%, which is 30.0% when rounded to the nearest whole number.

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