Gas Law Problem

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[Hikari]

A mouse is placed in a sealed chamber with air at 758 torr. This chamber is equipped with enough solid KOH to absorb any CO2 and H2O produced by the mouse. the gas volume in the chamber is measured to be exactly 2.60L and the temperature is held constant at 303K. After two hours, the pressure inside the chamber falls to 719.1 torr. What mass of oxygen has the mouse consumed?

Well, I found the volume Oxygen after the pressure drop to be 2.74L.

Then, I used ideal gas law to find the number of mols of oxyen present both before and after the pressure drop.

Before:
R = 62.37 L torr mol^-1 K^-1
V = 2.60L
T = 303K
P = 758 torr
 n = (758 torr)(2.60L)/(303K * 62.37) = .104285 mols

After:
R = 62.37 L torr mol^-1 K^-1
V = 2.74L
T = 303K
P = 719.1 torr
 n = (719.1 torr)(2.74L)/(303K * 62.37) = .10426 mols

I subtracted the mols after from the mols before and then multiplied by the molar mass of oxygen (32 g) to get 8e-8 grams of oxygen that was consumed by the mouse, but that answer is wrong wrong. Can somebody give me a hint as to why I'm not getting the right answer?

[Hikari]

Oh, that helps. Thank you very much!