 Physics Help Forum How do I determine the amount of water in a sealed container to create a given pressu
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 New Users New to PHF? Post up here and introduce yourself! Dec 12th 2016, 12:11 AM #1 Junior Member   Join Date: Dec 2016 Posts: 1 How do I determine the amount of water in a sealed container to create a given pressu I have a sealed container with a volume of 1 liter. I want to go from an initial pressure of p1=1 atm and an initial temperature of T1=298 to a final pressure of p2=10 atm and a final temperature of T2=453 K. I want to to use water to create the pressure. But I do not know how to determine the amount of water, how would I do that? Thanks. Last edited by bigbear312; Dec 12th 2016 at 12:14 AM.   Dec 13th 2016, 11:09 AM #2 Physics Team   Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,354 You can set up two equations in two unknowns: 1. For the initial condition you have gaseous air plus liquid water in the container. The number of moles of air from the Ideal Gas law is: $\displaystyle n_{a} = \frac {P_1 V_{a}}{RT_1}$ where $\displaystyle n_a$ is the number of moles of air and $\displaystyle V_{a}$ is the volume of air in the container. The volume of water at this stage is then $\displaystyle V_{w} = V - \rho_{w} n_w$ where V = size of the container or 1 liter and $\displaystyle \rho_w$ is the density of water in terms of liter/mole. Combining these two equations: $\displaystyle n_a = \frac {P_1(V-\rho_w n_w)}{R T_1}$ 2. The second equation is at the higher temperature, when the water has turned to gaseous steam. From the Ideal Gas law: $\displaystyle n_a + n_w = \frac {P_2 V}{R T_2}$ So now you have two equation with unknowns $\displaystyle n_a$ and $\displaystyle n_w$.  Tags amount, container, create, determine, pressu, pressure, sealed, thermodynamic, water, water vapor Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post Anonymous General Physics 0 Mar 21st 2014 08:51 AM madatix Thermodynamics and Fluid Mechanics 5 Oct 23rd 2010 01:43 PM dexterjg Energy and Work 7 Jul 1st 2010 05:50 AM jordanleeburgess Light and Optics 0 Feb 2nd 2010 06:24 PM sirdarksol Thermodynamics and Fluid Mechanics 1 Apr 27th 2009 10:10 PM