tbillion wrote:1.36 is the number of atmospheres in the jug? what is an atmosphere 4.7 is atmospheric pressure? increasing the volume to place in the jug by 5 i get because i want 5 psi. where did the 1.36 and the 4.7 come from is where i am lost at this point. gases is new science to me.
Ino is pretty terrible at chemistry ( ), so I'll explain this a bit more thoroughly.
One atmosphere is equivalent to 14.7PSI absolute pressure. You are looking to raise the internal pressure in the jug to 5PSI gauge pressure, which is the differential between the interior of the container and the atmosphere. This can also be expressed as 19.7PSI absolute pressure.
Dividing the absolute pressure after the addition by the initial (atmospheric) pressure will give you the ratio of the final pressure to the starting pressure, which is actually 1.34, not 1.36 as was stated above.
Finally, multiplying this ratio (1.34) by the starting volume (5L) and subtracting the initial volume gives you the final atmospheric pressure gas volume equivalent which must be added to the vessel in order to raise the pressure by 0.34atm (5PSI).
V<sub>addition</sub> = (1.34*5L) - 5L
V<sub>addition</sub> = 1.7L
Using Boyle's law is much simpler, but the above approach is more intuitive.
EDIT: Also, way to kick up a 5 year old thread, for a second I thought BLB had actually returned to the forum.