Question

How many moles of `CO_2` (g) are in a 5.6 L sample of `CO_2` measured at STP?

Answer 1

`"moles"=0.25`

Explanation:

Using the ideal gas equation, we can solve for the number of moles:

`PV=nRT`

where:
`P=`pressure
`V=`volume
`n=`moles
`R=`universal constant `(8.314(kPa*L)/(mol*K))`
`T=`temperature (Kelvin)

Recall that at STP conditions:

`P=101.325` `kPa`
`T=273.15` `K`

To solve for the number of moles of carbon dioxide gas, substitute your known values into the ideal gas equation:

`PV=nRT`

`n=(PV)/(RT)`

`n=((101.325kPa)(5.6L))/((8.314(kPa*L)/(mol*K))(273.15K))`

`n=((101.325color(red)cancelcolor(black)(kPa))(5.6color(orange)cancelcolor(black)(L)))/((8.314(color(red)cancelcolor(black)(kPa)*color(orange)cancelcolor(black)(L))/(mol*color(green)cancelcolor(black)(K)))(273.15color(green)cancelcolor(black)(K)))`

`n=0.2498580892` `mol`

`n=0.25` `mol` (rounded to `2` significant figures)

`:.`, there are `0.25` `mol` in `5.6` `L` of `CO_(2(g))` at STP conditions.