## MCAT Question A Day - 10/22/14 - Answer!

**What is the percent by mass of carbon in CO**

_{2}?

**A.**12%

**B.**27%

**C.**33%

**D.**

**44%**

*B is correct. C has 12 g / mol and 0 has 16 g / mol. The total weight of CO, is 44 g / mol. Carbon's weight divided by the total weight is 12 / 44= 0.27. We multiply by 100 to get 27%.*

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