Exam Suggested Solutions

[polky]

can u please put up question 3 for the multiple choices

Question 3 for MCQ: There's this thing with 5 carbons in it, and the carbons make up 40% of the mass.

M for 5 carbons = 5x12 = 60.

If 60g/mol is 40%, 100% will be (60/40) x 100 = 150g/mol

[annie]

Mao, for Question 16, did the question have a requirement on those isomers? In particular, I'm looking for "straight-chain" isomers, because cyclopentane is also another structural isomer.

Of course, there are also some geometric isomers, but they aren't structural isomers, nor are they on the course. A clever forum member just PM'd me about this.

I was about to say, I answered D for that question. There is a sixth isomer in which one Carbon has four carbons coming off it surely?

That isomer, with one carbon in the middle and 4 other carbons coming off it, has to have 11 hydrogens.  Thus it's not an isomer.

I didn't think of cyclopentane

Nah your're right, apparently the latest update of question 16 was that the question specfically stated you have to have a double bond present..

[bucket]

for 6A on the short answer, I put aminoethane instead of ethylamine, thats correct yeah?

[username]

Oh and thanks Mao, for doing all this.

[higbvuyb]

for 6A on the short answer, I put aminoethane instead of ethylamine, thats correct yeah?

I think aminoethane is the correct IUPAC name.


@Mao: could you tell me the options for multiple choice question 16, please?

[polky]

q16: the options were
a) 3
b) 4
c) 5
d) 6

If i remember correctly

[vce01]

for the disulfide links...

-c-s-s-c- would be okay wouldnt it??

[bucket]

i did R-S-S-R
lol
I'm thinking I shouldve like put the abbreviation of the amino acids.

[monicak]

for 6A on the short answer, I put aminoethane instead of ethylamine, thats correct yeah?

hmm that's what I wrote as well.. Hope it's right

[vce01]

what if you wrote ethanamine???

[username]

Pahahha I wrote ethamine.

[vce01]

oh btw, options and question for MC 20 as well please, thanks

[Collin Li]

Pahahha I wrote ethamine.

This is wrong.

Ethanamine, ethylamine or aminoethane are acceptable.

This site shows all the synonyms of this molecule: http://www.chemindustry.com/chemicals/651358.html

The way I remember whether it is ethanamine or ethamine is because the "an" in ethanamine indicates that it is saturated. If I was talking about ethenamine, how could I represent that in the shorter name? Ethemine? Hehe.

[monicak]

Here's a link to a site with the proper IUPAC amine naming system:
http://www.acdlabs.com/iupac/nomenclature/79/r79_510.htm

[ganges]

I need help...........


You know the question where it said why ethanol dissolves in water and petrol?

Well i said Because the OH bond forms a hydrogen bond in water and the non polar end of the hydrocarbon interacts with the non polar part of petrol.
But this is where i screwed up, for some stupid reason i also added that its a dipole dipole at the end.
Now i answered the 2 points correctly, however i added something wrond and irrelevant(dipole part) to it do i lose marks for adding something wrong to something that was right? The question was 2 marks btw.