steven2984 - 21-10-2002 at 06:53
Text Blue hey everyone!
I need some help w/ this partial pressure stuff that has me stumped
here's a type of problem i'm talking about : partial pressure I'm stuck i dont know the steps to finish it even tho they do give some steps there.
thanks for any help
steven2984 - 21-10-2002 at 06:55
sorry, here's the right link:click
Combined Gas Equation
Vaylo - 31-10-2002 at 20:21
Heh, it's been a while since I've had to deal with these things..
Basically, you just solve the Combined Gas equation (a combination of Boyle's Law and Charles' law) with the information you already have. The
equation is:
p1V1 over T1 = p2V2 over T2
Temp. must be in deg.Kelvin, the other units can be any pressure/volume measurement, so long as they are the same on both sides of the equation
So, for the blue gas from the site, you've got P1=9atm, V1=5L, P2=?, V2=15L and no change in temperature.
Substituting into the Combined Gas equation, you get
9atm * 5L = p2atm * 15L
45/15=p2
P2=3 atm
Doing the same for the red gas, you get a partial pressure of 4atm
Dalton's Law of Partial Pressures just states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of each gas,
or
ptotal=p1+p2+p3+p4...
These gasses are ideal, which means that the molecules of the two gasses will behave independantly of each other when combined (ie, they won't react
and form a new molecule)
So, now that you have the two partial pressures of the system, you can work out the total pressure of the system by simple addition, and you get the
total pressure of your system to be *drumroll*
7atm.
There are other, more tedious ways of solving these equations, but these require assumptions of temperatures and such, so it's easiest just to stick
to the method which uses only the information you've been given...
Anyways, hope this helps
Vaylo
steven2984 - 1-11-2002 at 07:48
thank you for replying. my textbook either missed covering the Combined Gas Law or something, but i have another question dealing with that. How would
u solve a problem when you're given the mass of the gas, the volume, and the temp.?
I'm asking b/c looking at the Combined Gas Law i see that i wouldn't be able to plug in the mass since its not a variable.
Here's the problem:
A mixture of 1. 00 g H2 and He is placed in a 1.00-L container at a temperature of 27 C. Calculate the partial pressure of each gas and the total
pressure
Steve
steven2984 - 1-11-2002 at 07:50
Edit: 1.00 g H2 and 1.00 g He
vulture - 1-11-2002 at 09:50
You'll need to use this equation:
pV = nRT
n = number of moles
R = 0,082
You can remodel this equation in anyway to isolate the variable of your choice.
steven2984 - 4-11-2002 at 08:46
Thanks you! I get it now!!wooho!!!