Question

How do you calculate the density of butane,(C4H10) at STP??

Answer 1

`2.59xx10^-3"g cm"^-3` or `2.59"kg m"^-3`

`"density"="mass"/"volume"` so let's find a mass and a volume!

Explanation:

We will use the fact that, at STP (`0^@C` and 1atm), 1 mole of an ideal gas occupies `22.4"dm"^3`

This means 1 mole of butane has a volume of `22.4"dm"^3` at STP.

`:.v=22.4"dm"^3`
`=22.4xx10^3"cm"^3`
`=22.4xx10^-3m^3`

1 mole of butane has the same mass in grams as its relative molecular mass.

`M_r=4xx12+10xx1`
`=58`

`:. m=58g=58xx10^-3kg`

Using `rho=m/v` where `rho` is density:

`rho=58/22.4xx10^3`
`=2.59xx10^-3"g cm"^-3` or `2.59"kg m"^-3`