# Question 351ba

Sep 4, 2017

$0.100$ $\text{mol O}$

#### Explanation:

We're asked to find the number of moles of oxygen in an unknown compound containing $\text{C}$, $\text{H}$, and $\text{O}$, given that $3.00$ $\text{g}$ of this compound underwent complete combustion.

We're given that the compound contained $0.100$ $\text{mol C}$ and $0.200$ $\text{mol H}$. Let's convert these values to grams using the molar mass of the elements:

0.100cancel("mol C")((12.01color(white)(l)"g C")/(1cancel("mol C"))) = 1.201color(white)(l)"g C"

0.200cancel("mol H")((1.01color(white)(l)"g H")/(1cancel("mol H"))) = 0.202color(white)(l)"g H"

The mass of the compound was given as $3.00$ $\text{g}$. Since oxygen is the only other element in the compound, the mass of oxygen is

$3.00 \textcolor{w h i t e}{l} \text{g" - 1.201color(white)(l)"g C" - 0.202color(white)(l)"g H" = color(red)(ul(1.597color(white)(l)"g O}$

We can find the moles of $\text{O}$ using its molar mass:

color(red)(1.597color(white)(l)"g O")((1color(white)(l)"mol O")/(16.00cancel("g O"))) = color(blue)(ulbar(|stackrel(" ")(" "0.100color(white)(l)"mol O"" ")|)#