**Step 1: **62.1% C, 5.21% H, 12.1% N, and the remainder O by mass.** **Recall that ** mass percent** is given by:

$\mathbf{100}\mathbf{\%}\mathbf{=}\mathbf{\%}\mathbf{C}\mathbf{+}\mathbf{\%}\mathbf{H}\mathbf{+}\mathbf{\%}\mathbf{N}\mathbf{+}\mathbf{\%}\mathbf{O}\phantom{\rule{0ex}{0ex}}\mathbf{100}\mathbf{\%}\mathbf{=}\mathbf{62}\mathbf{.}\mathbf{1}\mathbf{\%}\mathbf{+}\mathbf{5}\mathbf{.}\mathbf{21}\mathbf{\%}\mathbf{+}\mathbf{12}\mathbf{.}\mathbf{1}\mathbf{\%}\mathbf{+}\mathbf{\%}\mathbf{O}\phantom{\rule{0ex}{0ex}}\mathbf{\%}\mathbf{O}\mathbf{=}\mathbf{100}\mathbf{\%}\mathbf{-}(62.1\%+5.21\%+12.1\%)\phantom{\rule{0ex}{0ex}}\mathbf{\%}\mathbf{O}\mathbf{=}\mathbf{100}\mathbf{\%}\mathbf{-}\mathbf{79}\mathbf{.}\mathbf{41}\mathbf{\%}$

** % O = 20.59%**

$\overline{){\mathbf{\%}}{\mathbf{}}{\mathbf{mass}}{\mathbf{=}}\frac{\mathbf{mass}\mathbf{}\mathbf{of}\mathbf{}\mathbf{X}}{\mathbf{total}\mathbf{}\mathbf{mass}}{\mathbf{\times}}{\mathbf{100}}}$

Assuming we have **100 g** of the compound, this means we have **62.1 g C, 5.21 g H, 12.1 g N, and 20.59 g O**.

Determine the empirical formulas of the compounds with the following compositions by mass.

62.1% C, 5.21% H, 12.1% N, and the remainder O

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