Question

What is the density of `NH_3` gas at 435 K and 1.00 atm?

Answer 1

From the ideal gas equation: `n/V=(P)/(RT)`. Agreed? And we assume ideality for ammonia gas (good enuff for a first approx.).
We get `rho~~0.5*g*L^-1`

Explanation:

But `n="Mass"/"Molar mass"`.

Thus `"Mass"/"Molar mass"=(PV)/(RT)`

And on rearrangement, `"Mass"/"V"=(P)/(RT)xx"Molar mass"`

But, by definition, `"density, "rho="Mass"/"Volume"=(P)/(RT)xx"Molar mass"`

`=(1.00*cancel(atm)xx17.03*g*cancel(mol^-1))/(0.0821*L*cancel(atm)*cancel(K^-1)*cancel(mol^-1)xx435*cancelK)=`

`??g*L^-1`

So this expression gives us an answer in `g*L^-1` as required for a density.