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I'm given a container of volume of 4.0 Litres that containes Nitrogen at $25 ^\circ C $ and 803 kPa. This container is connected by a valve to another container of 10.0 litres volume that containes Aragon at $25 ^\circ C $ and $47.2 kPa $ .

We now open the valve so that the two gas are mixing .

I need to calculate the partial pressure of every gas after the mixing and the total pressure of the mixture.

My question is - using the Dalton's law of partial pressures , isn't the partial pressure of every gas if excatly $803 kPa $ and $ 47.2 kPa $ and the total pressure if $ 803+47.2 kPa$ ?

What am I missing here?

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Dalton's law of partial pressures means that the total pressure in the final volume $V=V_1+V_2$ is equal to the sum of the partial pressures P(N2) + P(Ar) in this volume. However, the partial pressure of N2 in the total volume $V$ is not the same as the pressure of N2 in its initial volume $V_1$. You have to account for the expansion. This probably means you also need to use the ideal gas law for that.

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  • $\begingroup$ Is that pressure applied on gas or applied by gas? $\endgroup$ – Sufyan Naeem Dec 17 '15 at 18:16

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