# Why 1 liter * atm = 101.33 joules ?

1. Dec 14, 2016

### Tahira Firdous

Hi !! I have been searching but i am not able to find out that is there any reason behind , why 1 liter * atm = 101.33 joules ?

2. Dec 14, 2016

### Staff: Mentor

Are you asking why it comes out equal to 101.33 Joules, or why a pressure (atm) time a volume (liter) gives an energy (joules)?

3. Dec 15, 2016

### Tahira Firdous

I am asking that why it is equal to 101.33 joules any logical reason or just a constant ?

4. Dec 15, 2016

### Daniel Hendriks

5. Dec 15, 2016

### Tahira Firdous

6. Dec 16, 2016

### nasu

Even though this is not wrong, is just shifting the question to why 8.31 J equals 0.082 L*atm.
You could just go directly to change the units for pressure and volume to SI units and get the answer.
$1 atm =1.01 \times 10^5 N/m^2$
$1L =10^{-3} m^3$
So
$1 atm \times 1L = 101 N \cdot m$ or 101 J

7. Dec 17, 2016

### CWatters

+1

Consider a piston of area A moving in a cylinder with constant pressure...

Work = Force * displacement ............ (1)

Pressure = Force/Area
so
Force = Pressure * Area ....................(2)

sub for force in (1) gives...
Work = Pressure * Area * displacement ..............(3)

then recognise that
ΔVolume = Area * displacement

so
Work = Pressure * ΔVolume