(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 0.250-g sample of a magnesium-aluminum alloy dissolves completely in an excess of HCl(aq). When the liberated H2(g) is collected over water at 29C and 752 torr, the volume is found to be 313 mL. The vapor pressure of water at 29C is 30.0 torr.

2. Relevant equations

PV = nRT

Al = 26.98 g/mol

Mg = 24.31 g/mol

3. The attempt at a solution

I'm unsure how to do this...but here's what I did.

1) First I converted everything.

752 torr = 0.989 atm

313 mL = 0.313 L

29C = 302K

2) Then I used the forumla PV = nRT to find out how many moles of water there was.

3) Then I multiplied the moles by the MM of Al and Mg.

4) Finally I did .3038x + .3371(1-x) = 250 and got a whole number above 100% which means that my answer was wrong.

I haven't used any the information about the vapor pressure of water because I dont know what to do with it...

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# Mass % of an alloy

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