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**[SOLVED] Pressure/Mass Relationship**

**1. Homework Statement**

[tex]H_{2}[/tex] gas was obtained by the displacement of [tex]H_{2}O[/tex] at total pressure of 833 torr. The volume of the obtained gas was .5 Liters and the vapor pressure of [tex]H_{2}O[/tex] was 22 torr. Find the mass of [tex]H_{2}[/tex] gas.

**2. Homework Equations**

[tex]P_{tot} = P_{1} + P_{2}[/tex]

[tex] P_{tot} = (n_{1} + n_{2})(\frac{RT}{V})[/tex]

[tex] P_{1} = (n_{1})(\frac{RT}{V})[/tex]

[tex] P_{2} = (n_{2})(\frac{RT}{V})[/tex]

**3. The Attempt at a Solution**

Now here is my attempt, which I'm definitely not sure of:

[tex]P_{tot} = P_{H_{2}O} + P_{H_{2}} \Rightarrow P_{H_{2}} = 833 - 22 = 811[/tex]

Then,

[tex]n_{H_{2}} = \frac{PV}{RT} = \frac{(811)(0.5)}{(0.082)(295)} = 16.7[/tex]

And then trivially obtain the mass of hydrogen in the experiment:

[tex]m_{H_{2}} = (2)(16.7) = 33.4 g[/tex]

Is this correct? I'm not sure of how I obtained [tex]P_{H_{2}}[/tex].

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