Chemistry Chapter 5 - End of Chp Test

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bbiebelberg
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Joined: Thu Jan 09, 2020 8:28 pm

Chemistry Chapter 5 - End of Chp Test

Post by bbiebelberg » Sun Jan 26, 2020 4:11 pm

Hello!  I have two questions about the Chem Chp 5 end-of-chapter test.

Question 1
The last paragraph in the passage lists chloroform as a nonpolar anesthetic.  While I agree that none of the other choices to Question 1 have nonzero dipoles, why would the passage state chloroform is nonpolar if it in fact has a net dipole moment?  This caused confusion.

Question 4 (the second one.. so Q11 overall).
The answer states that rates of effusion depend on molar mass, show in Graham's law.  There is no Graham's law or discussion of effusion and molar mass in Chapter 5.  Are we expected to know laws/relationships that are not presented in the chapter?   

(Separately, since the mole fractions and partial pressures of the two gasses are the same, I would have thought they would effuse at the same rate.)

Thank you.
NS_Tutor_Mathias
Posts: 616
Joined: Sat Mar 30, 2019 8:39 pm

Re: Chemistry Chapter 5 - End of Chp Test

Post by NS_Tutor_Mathias » Mon Jan 27, 2020 6:29 pm

Question 1:
Chloroform simply has a very small dipole moment. Because that moment is so small, it effectively acts as a non-polar anesthetic. This is a good question in that it highlights the potential for mismatches between categorization and actual molecular-scale physicial properties of a substance.

Independent Question 4:
This is indeed an oversight. Graham's law may appear on the MCAT, or at least be tested in a qualitative way (know that heavier gasses diffuse slower). Generally chapters aim to be comprehensive, and issues like these are why we constantly work to improve our materials.
bbiebelberg
Posts: 19
Joined: Thu Jan 09, 2020 8:28 pm

Re: Chemistry Chapter 5 - End of Chp Test

Post by bbiebelberg » Sat Feb 01, 2020 8:38 pm

Thank you, Mathias!
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