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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: spunkee on February 25, 2005, 11:09:37 PM

Title: PV=nRT problem (i think?!).
Post by: spunkee on February 25, 2005, 11:09:37 PM

Well, I am in general chemistry 2 at a community college and I know I should probably be able to this problem but I am stuck.

"Write an equation for the production of Hydrogen (H2) from the reaction of zinc metal and hydrochloric acid. How many grams of zinc are required to make one liter of hydrogen gas at STP according to the reaction?"

I have figured out the equation:
Zn(s) + 2HCL(aq) --> H2(g) + ZnCl2(aq)

Now I've started doing the rest of the problem and I began by plugging in 1 Liter to PV=nRT and solving for the number of moles which gives me .045 mol Zn. Do I simply use mol ratio and then convert mol of Zn to mol of H2 and then to grams of H2, or am I way off? I think I am really messing something up but I am not sure. Any help is much appreciated  :D

Title: Re:PV=nRT problem (i think?!).
Post by: Mitch on February 25, 2005, 11:33:01 PM

PV=nRT is only meant for gases. Why are you using it for Zinc?

Solve it for Hydrogen and then use mole fractions to get the moles of zinc needed. I think the answer should still be the same however as you already calculated.

Title: Re:PV=nRT problem (i think?!).
Post by: spunkee on February 25, 2005, 11:50:15 PM

Ok, thank-you so much for the help. I realize now that I switched my zinc and hydrogen around, and I'm sure it should be the same answer. Thanks again  :)