Recall that in ** combustion analysis**, a compound reacts with excess O

For a compound composed of C, H, and O, the reaction looks like this:

C** _{x}**H

*mole-to-mole comparison:*

**1 mole of C**in**1 mole of CO**_{2 }*(molar mass = 44.01 g/mol or mg/mmol)***2 moles of H**in**1 mole of H**_{2}O*(molar mass = 18.02 mg/mmol)*

Finding the mass of C and H:

$\mathbf{mass}\mathbf{}\mathbf{of}\mathbf{}\mathbf{C}\mathbf{=}\mathbf{6}\mathbf{.}\mathbf{95}\mathbf{}\overline{)\mathbf{mg}\mathbf{}{\mathbf{CO}}_{\mathbf{2}}}\mathbf{\times}\frac{\mathbf{1}\mathbf{}\overline{)\mathbf{mmol}\mathbf{}{\mathbf{CO}}_{\mathbf{2}}}}{\mathbf{44}\mathbf{.}\mathbf{01}\mathbf{}\overline{)\mathbf{mg}\mathbf{}{\mathbf{CO}}_{\mathbf{2}}}}\mathbf{\times}\frac{\mathbf{1}\mathbf{}\overline{)\mathbf{mmol}\mathbf{}\mathbf{C}}}{\mathbf{1}\mathbf{}\overline{)\mathbf{mmol}\mathbf{}{\mathbf{CO}}_{\mathbf{2}}}}\mathbf{\times}\frac{\mathbf{12}\mathbf{.}\mathbf{01}\mathbf{}\mathbf{mg}\mathbf{}\mathbf{C}}{\mathbf{1}\mathbf{}\overline{)\mathbf{mmol}\mathbf{}\mathbf{C}}}$

mass of C = 1.897 mg C

$\mathbf{mass}\mathbf{}\mathbf{of}\mathbf{}\mathbf{H}\mathbf{=}\mathbf{2}\mathbf{.}\mathbf{84}\mathbf{}\overline{)\mathbf{mg}\mathbf{}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}}\mathbf{\times}\frac{\mathbf{1}\mathbf{}\overline{)\mathbf{mmol}\mathbf{}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}}}{\mathbf{18}\mathbf{.}\mathbf{02}\mathbf{}\overline{)\mathbf{mg}\mathbf{}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}}}\mathbf{\times}\frac{\mathbf{2}\mathbf{}\overline{)\mathbf{mmol}\mathbf{}\mathbf{H}}}{\mathbf{1}\mathbf{}\overline{)\mathbf{mmol}\mathbf{}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}}}\mathbf{\times}\frac{\mathbf{1}\mathbf{.}\mathbf{01}\mathbf{}\mathbf{mg}\mathbf{}\mathbf{H}}{\mathbf{1}\mathbf{}\overline{)\mathbf{mmol}\mathbf{}\mathbf{H}}}$

mass of H = 0.318 mg H

**mass of O** = 3.06 mg – (1.897 mg C + 0.318 mg H) = 0.8446 mg O

The characteristic odor of pineapple is due to ethyl butyrate, a compound containing carbon, hydrogen, and oxygen. Combustion of 3.06 mg of ethyl butyrate produces 6.95 mg of CO_{2} and 2.84 mg of H_{2} O. What is the empirical formula of the compound?

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