Two cylinders at 27C are connected by a closed stopcock ystem. One cyclinder contains 2.4 L of hydrogen gas at o.600 atm; the other cylinder contains 6.8L of helium at 1.40 atm. Assume valve take up no room.

what is the total pressure when the valve is open ?
I don't know how to find the total pressure
(0.600 atm)(L)/(0.0821)(300K)=5.846x10^-2
n=(1.40 atm)(6.8L)/(0.0821)(300k)=3.865x10^-1
Total pressure =(n1+n2..)(RT/V)

I responded to your original post and asked, "what is your question?"

Isnt PV a constant in both continers?

Then the sum of P1V1 + P2V2 is a constant.

So PfinalVfinal=P1V1+P2V2
pfinal= (p1v1+P2v2)/(v1+V2)
=(.6*2.4 + 1.4*6.8)/9.2 atm
= 1.19 atm Compare that to what you got.

My question is how do I find the total pressue, I found the number of moles for each situation do i add them and plug it into the Total pressure =(n1+n2..)(RT/V)

This is what I have is this correct, if so then I do not know what to do after ths.
(0.44496)(27)(0.0821)/V(I do not know what to plug in here

for V, the sum of the initial volumes.

Yes, you are doing it ok although it's a little longer than the way Bob Pursley has worked it.

P = nRT/V =
n = n1 + n2 = ok
R is ok.
T must be changed to 300 K.
V = 2.4 L + 6.8 L = 9.2 L.
And the answer comes out to 1.19 atm as Bob Ps post indicates.

To find the total pressure when the valve is open, you need to calculate the total number of moles of gas in both cylinders and then use the ideal gas law equation:

PV = nRT

where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature.

Let's calculate the number of moles of hydrogen gas first:

n1 = (P1 * V1) / (R * T)
= (0.600 atm * 2.4 L) / (0.0821 atm L/(mol K) * 300 K)
≈ 0.144 mol

Now, let's calculate the number of moles of helium gas:

n2 = (P2 * V2) / (R * T)
= (1.40 atm * 6.8 L) / (0.0821 atm L/(mol K) * 300 K)
≈ 0.335 mol

The total number of moles of gas is the sum of n1 and n2:

ntotal = n1 + n2
= 0.144 mol + 0.335 mol
≈ 0.479 mol

Finally, we can calculate the total pressure when the valve is open using the ideal gas law:

Ptotal = (ntotal * R * T) / V
= (0.479 mol * 0.0821 atm L/(mol K) * 300 K) / (2.4 L + 6.8 L)
≈ 0.161 atm

Therefore, the total pressure when the valve is open is approximately 0.161 atm.