Question

If the density of an unknown gas `Z` 4.50 g/L at STP, what is the molar mass of gas `Z`?

Answer 1

`P.MM= d.R.T`

Explanation:

Use the ideal gas equation

`P.V=n.R.T`

`P.V= m/(MM).R.T`

`P.MM= m/V.R.T`

`P.MM= d.R.T`

`P" is the pressure of the gas (" atm")"`
`MM" is the molar mass ("g.mol^-1")"`
`d" is the density of the gas ("g.L^-1")"`
`R" is the universal gas constant ("0.0821*L.\atm.mol^-1.K^-1")"`

Solve for `MM`

`MM= (d.R.T)/P`

`MM=(4.50*g*L^-1* 0.0821*L*atm*mol^-1*K^-1*273*K)/(1.00*\atm)`

`MM ~= 101" "g.mol^-1`