Homework Help: CHEM URGENT PLZ

Posted by Anita on Friday, May 9, 2008 at 9:17pm.

1.Which of these substances has bent molecular geometry around the oxygen atom? Multiple correct answer may apply.

a.water
b.isopropyl alcohol (rubbing alcohol)**
c.acetone**
d.diethyl ether.

2.Which of these species are polar? Ignore slightly polar C-H bonds. Multiple correct answers may apply.

a.water **
b.isopropyl alcohol (rubbing alcohol)
c.acetone **
d.diethyl ether.

3.Which of these substances has the ability to hydrogen bond to itself Multiple correct answer may apply.

a.water **
b.isopropyl alcohol (rubbing alcohol)
c.acetone **
d.diethyl ether.

4.At a temperature of 35.0 慢, 19.3 kJ of thermal energy will make 33.0 g of acetone evaporate. Calculate the heat of vaporization of acetone at 35.0 慢 in units of kJ/mol.
I am confused on how to use the equation.

Please check my answers for the other ones.....There my be more than one answer.

CHEM URGENT PLZ - DrBob222, Friday, May 9, 2008 at 10:01pm
I may not be much help here because I'm confused on some of the questions. So take my help as advice and look for other sources.
#1.
I know what bent means. Water, which you have checked, is correct. But all of the organic molecules below water are bent also, in the sense that none of them are linear compounds. I would check all of them but I don't think that is the spirit of the question.

#2.
Water, which you have checked, certainly is polar and that answer is correct. But then the questioner says we are to ignore the polarity between bonds such as C-H and the confusion begins again. How much is too much to ignore. In my opinion, all of them are polar; they all have a dipole moment.

#3.
Water and isopropyl alcohol can form hydrogen bonds. It is true that both acetone and diethyl ether have the very negative C=O structure; however, there is no hydrogen attached directly to them. There may be some slight tendencies to form H bonding with the H attached to the C atoms but this is weak. I think most organic chemists will say that diethyl ether and acetone do not form H bonds.

#4.
It would have been helpful if you had shown what formula you don't know how to use.
q = mass x delt H vap.
You are given q, which I would leave in kJ. You are given mass in grams, that should be changed to moles of acetone. Solve for delta H vap. I hope this helps.

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