Question

I have a problem, and I have the answer but I don't know where the solution comes from. ( I have to be able to solve these myself so please help me by answering the questions about the problem.)

Here is the answer given to me by the professor:

What is the density of SF₄ vapor at 650 torr and 100 C?

650 torr (1atm/760 Torr)=0.855atm 100C=373K

PV=nRT n/v=P/RT= 0.855atm/0.8206l-atm/molek) (373)=0.0279 mole/l

M.W. of SF₄=108.1 gm/mole

Density=mass/volume 0.0279 mole/l(108.1gm/mole)

Answer =3.02 gm/l

Here are my questions:

Where did the 760 torr come from? Where did the 0.855atm come from? What is the abbreviation m.w. ? I basically need a step by step explanation of this problem because I dont understand how the answer was achieved.

Answer 1

SF4 vapor at 650 torr and 100 C?

Vapour pressure of SF4 = 650 torr                               (1atm = 760 Torr)

                                         = 0.855atm

T = 100C = 373K ( c+ 273 = K)

fro ideal gas equation

PV=nRT

n = no of moles of gas = wt/mwt

PV = WtRT/Mwt

PMwt = (w/v)RT

(w/v) = density = d

d = P*Mwt / RT

p = pressure = 0.855atm

R = ideal gas constant = 0.0821 l.atm.k-1.mol-1

molarmass of SF4 = M.Wt = 108.1 gm/mole

density = (0.855*108.1)/(0.0821*373)

        = 3.02 gram/l

        = 0.00302 gram/ml