Partial Pressure?

Question

An apparatus consists of a 4L flask containing Nitrogen gas at 19degrees C and 780 kPa, joined by a valve to a 7 L flask containing argon gas at 19degrees C and 40.8 kPa. the valve is opened and the gases mix. What is the partial pressure of the nitrogen after mixing? Use units of kPa.

i found the moles of each gas, and used the proportion moles of gas over total moles, multiplied by total pressure.
im thinking this is wrong.
how do i do this?

well, dimos, i got 298.47 kPa...
hm.

Answer 1

The moles of N2, from the state equation of gases are:

n1 = P1*V1/R*T

In the joined flask the N2 pressure (partial pressure) is:

p = n1*R*T/(V1+V2)

p = (P1*V1/RT)*R*T/(V1 + V2)

p = p1*V1/(V1 + V2)

p = 780*4/(4 + 7), p = 283.64 kPa (approx.)