# Chapter 3 - Chemical Compounds - Exercises - Percent Composition of Compounds - Page 104: 20

36.18%

#### Work Step by Step

Using the molar mass, it follows: Mass percent O= $\frac{5\,mol\,O\times\frac{15.999\,g\,O}{1\,mol\,O}}{221.1\,g\,malachite}\times100\%$ $=36.18\%$

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