Wednesday
April 1, 2015

Homework Help: chemistry

Posted by terrence on Wednesday, August 31, 2011 at 6:51am.

I'm having a problem with the gas constant. This is it:


In the question: Calculate the amount of moles of a gas if .455 occupies a volume of 250mL at 27 degrees Celsius and 772mmHg.

I do all the correct steps using the R = 8.314 for the 772mmHg. I get .077 for this, which is incorrect.
Then I do the same thing but convert the 772mmHg to 1.016atm and for the gas constant use .08206. I get .0103 which is the correct answer. Why does it make a difference which I used? In fact i tried using the larger constant with units of Pa in a question and didnt get it right, but did it again with the smaller constant in units atm and got it right. Please please help this confusion. Thanks

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