# Homework Help: Getting strange answer , lease help

1. Aug 10, 2006

### xto

The question is
a volume of 2.2m^3 of air at inital conditions of 1.2bar and 303K undergoes the following process to complete a cycle :

i)isothermal compresssion from state 1 through a volumetric compression ration of 6 to state 2

ii) isobaric expansion from state 2 back to the initial volume thus reaching state 3

iii) isochoric cooling from state 3 back to the original pressure to reach state 1

Q1) Find the mass of air present

so i use the formula PV=nRT

P=1.2bar
V=2.2M^3
n=?
R=6
T=303K

so i need to find N so i got 2.64 = 1818N
which N is 1.452x10^-3
which is total not the mass of the air , please help

2. Aug 12, 2006

### FredGarvin

R is the universal gas constant. It is not 6.

3. Aug 12, 2006

### Staff: Mentor

OMG, I just spit water all over my keyboard. :rofl:

4. Aug 12, 2006

### xto

ok , i kind of get it
beacuse i'm given 2 R
Rv is 6
the other R is 0.287kJ/kg K

so its

(1.1832)x(2.2x10^3)
---------------------
(0.287)x(303k)

then i get 29.90g (to 2d.p) Air

is that right for the mass of air present?

By the way , thank you so much for the help