<p>Hi, I'm taking the test in 2 days and I've been cramming like crazy,
I took the official practice test today (big blue book) and I have one main question, #65.
It gives you an experiment about collecting H gas using HCl and Mg metal. It gives you data (atmospheric pressure=749.8mm Hg, vapor pressure of H2O=19.8mm Hg, volume of H gas collected over water=25.2ml, water/room temp=22 C, mass of Mg=.024g)
Reaction is Mg(s) + 2H(+) --> Mg(2+) + H2(g).<br>
The question asks: "The volume of the dry hydrogen gas at 1 atm and room temperature would be"
Correct answer is C, ((25.2)(749.8-19.8)) / 760 mL. Could someone explain this to me? </p>
Why does mixing 1L He gas and 1L Ne gas in a 2L flask increase entropy?</p>
<p>In the first section there is also a set asking about precipitates from mixing Na2CrO4, PbCrO4, NaNO3, Pb(NO3)2 (given that they are solids, soluble/insoluble, color) and it asks for results when 2 of them are mixed in water. Would the color of the solution be determined by if there is excess of one solid after precipitation?</p>
<p>Lastly, how much does the test ask about "common" chemicals (like what chemical is in household bleach)?</p>
<p>(Also unrelated question, how hard is the US history SAT? I went through Barrons taking notes on what seemed important and skimmed through PR but my practice tests haven't been great. They seem to ask about authors and books as well as quotations and who said them. Any last minute tips or vital information I should know?)</p>