Question #351ba

1 Answer
Sep 4, 2017

0.100 "mol O"

Explanation:

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

We're given that the compound contained 0.100 "mol C" and 0.200 "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 "g". Since oxygen is the only other element in the compound, the mass of oxygen is

3.00color(white)(l)"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 "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"" ")|)