jane1234's chemistry questions!!

[nacho]

hey,
do we need to know, be able to explain quartenary structures?
or will they only ever ask for tertiary? (Proteins and such)

[tony3272]

hey,
do we need to know, be able to explain quartenary structures?
or will they only ever ask for tertiary? (Proteins and such)

My teacher said we just needed to know up to tertiary structures.

[luken93]

Yeah, primary secondary and tertiary only, not quantenary.

[Graphite]

Quaternary or tertiary, both can potentially have more than 2 non equivalent hydrogen environments

Nope. Quaternary carbons have 4 C-C bonds, and won't show up in 1H NMR. Tertiary carbons have 3 C-C bonds and 1 C-H.

Yep. You are correct, I forgot the need for a hydrogen for proton NMR!

[Andiio]

I haven't even heard of a quartenary structure of proteins and such LOL they aren't in any of my textbooks and possibly not in the study design either?
Jeebuz!

[lexitu]

Quaternary structure relates to the interaction between two or more polypeptide chains in a protein. Not sure if you need to know about it but it's a simple concept nevertheless. Many proteins have a quaternary structure because they have more than one polypeptide chain.

[luken93]

It is not in the study design - the more things we DON'T have to worry about the better people.

But if you really really want to know, read lex's explanation!

[Keki]

Having trouble understanding this question,

Checkpoints 2011 Q20

The mass of magnesium chloride, MgCl2, that would contain 0.25 mol of chloride ion, is closest to
A. 11.9g
B. 14.9g
C. 23.8g
D. 95.2g


(Ncl-)= 2 x n (MgCl2) = 0.25
n(MgCl2)= 0.125; Mass of (MgCL2)= 0.125x 95.2 = 11.9g

What I'm not understanding from the answer is,
If one Cl is 0.25 mol, how come MgCl2 is smaller than 0.25 when there's 2 Cl's in it :S

Thanks!

[Vincezor]

Having trouble understanding this question,

Checkpoints 2011 Q20

The mass of magnesium chloride, MgCl2, that would contain 0.25 mol of chloride ion, is closest to
A. 11.9g
B. 14.9g
C. 23.8g
D. 95.2g


(Ncl-)= 2 x n (MgCl2) = 0.25
n(MgCl2)= 0.125; Mass of (MgCL2)= 0.125x 95.2 = 11.9g

What I'm not understanding from the answer is,
If one Cl is 0.25 mol, how come MgCl2 is smaller than 0.25 when there's 2 Cl's in it :S

Thanks!

Okay think of it like this: and assume Cl is limiting.

[Keki]

Having trouble understanding this question,

Checkpoints 2011 Q20

The mass of magnesium chloride, MgCl2, that would contain 0.25 mol of chloride ion, is closest to
A. 11.9g
B. 14.9g
C. 23.8g
D. 95.2g


(Ncl-)= 2 x n (MgCl2) = 0.25
n(MgCl2)= 0.125; Mass of (MgCL2)= 0.125x 95.2 = 11.9g

What I'm not understanding from the answer is,
If one Cl is 0.25 mol, how come MgCl2 is smaller than 0.25 when there's 2 Cl's in it :S

Thanks!

Okay think of it like this: and assume Cl is limiting.

God damn, it took me 30 minutes to get my head around that T^T.
I kept thinking of the answer as mol + mol = greater number of moles instead of the two combining..

Next question:
One of molecule of butane (c4H10) would have a mass, in grams, of
=58/6 x 10^23

How come it's that and not m = n x M??

[Andiio]

Having trouble understanding this question,

Checkpoints 2011 Q20

The mass of magnesium chloride, MgCl2, that would contain 0.25 mol of chloride ion, is closest to
A. 11.9g
B. 14.9g
C. 23.8g
D. 95.2g


(Ncl-)= 2 x n (MgCl2) = 0.25
n(MgCl2)= 0.125; Mass of (MgCL2)= 0.125x 95.2 = 11.9g

What I'm not understanding from the answer is,
If one Cl is 0.25 mol, how come MgCl2 is smaller than 0.25 when there's 2 Cl's in it :S

Thanks!

Okay think of it like this: and assume Cl is limiting.

God damn, it took me 30 minutes to get my head around that T^T.
I kept thinking of the answer as mol + mol = greater number of moles instead of the two combining..

Next question:
One of molecule of butane (c4H10) would have a mass, in grams, of
=58/6 x 10^23

How come it's that and not m = n x M??

It asks specifically for one molecule, so you need to derive the number of moles from the 1 molecule of butane, i.e. n = # of molecules/Na(Avogadro's constant). Then you simply use m = n x Mm as per usual!

[Keki]

Thanks! I get what they were doing now -.-"
They gave a simplified answer :@ Darn checkpoints!!