What is the density of NH3 at ..?

Question

1.0526 atm and 298 K?



AND if the density of a gas is 1.2 g/L at 0.98 atm and 293 K, what is its molecular mass?


formula is PV=nRT R = 0.0821

i dont understand how to figure this out.
THANKS!

Answer 1

1) You know the definition of density:
........d = m/V.........(1)
where: d=density
.............m = mass
.............V = volume

2) Additionally, the mass:
........m = nM..........(2)
where: n = number of moles
.............M = molecular mass

3) We subsitute (2) in (1):

d = nM/V ........ we solve for n:

n = dV/M.....(3)

4) Substitute this result in your known Gas Law:

PV = nRT
PV =(dV/M)RT.... we can cancel V in both sides:

P = dRT/M........

we solve for d:

d = PM/RT -------> This is the expression that can give you the density of the gas given the other conditions.

Just use it to solve with your data! (This very same expresion can be used to solve the second part of the problem).

That´s it!

Good luck!