jane1234's chemistry questions!!

[luken93]

Nah, quite sure concordant = last 3/closest titres.

Do you mean R - NH - R? If so, it's a secondary amine.

[jane1234]

Nah, quite sure concordant = last 3/closest titres.

Do you mean R - NH - R? If so, it's a secondary amine.

So you always use closest three no matter how many you're given?

And the NH in DNA bases, so I guess its R - NH - R

[tony3272]

Okay just did Neap 2008:

1. When you have masses of a precipitate as 1.183g 1.137g 1.109g 1.110g and 1.108g, to find the average mass would you take all the values, or just the last three??? The answers say only the last three, but this doesn't even follow the titration +-0.05mL concordant results method. Would VCAA accept it if you used all 5?

2. Is an NH group considered an amine? Even though it only has one H?

Thanks

For 1. you don't include the first two because it's evident that the precipitate is not fully dry. I'm unsure as to why it went up from 1.109g to 1.110g though  

[tony3272]

Also their not titres, they're just precipitates. So the .05 mL rule doesn't apply.

[Water]

 1.109g 1.110g and 1.108g <<<<<<<<<<< Distortion of Mass could occur because of air weight I'd suspect, or slight machine errors since the mass difference is so little. Otherwise, they are constant.

[Andiio]

Sorry for bringing up the multiplicity issue again, but how do you know exactly when to either add or to multiply the adjacent (n+1) approximated peaks together?

My teacher told us that both would be fine as long as we explain what we did, but hmm..

[luken93]

Ha? You don't need to know about multiplicty and joining peaks for VCE?

[pi]

Ha? You don't need to know about multiplicty and joining peaks for VCE?

Pretty sure thats right

[Mao]

Sorry for bringing up the multiplicity issue again, but how do you know exactly when to either add or to multiply the adjacent (n+1) approximated peaks together?

My teacher told us that both would be fine as long as we explain what we did, but hmm..

Add. In VCE just add them together.

[DannyN]

sigh... i learnt multiplicity this year at tutor... so if we multiplied in the vce exam would it marked as wrong?

[nacho]

na, both are acceptable, and the same answer if there are <6 splits.

vcaa will never ask these q's because different schools teach different methods,
furthermore it's pretty ambiguous with all those little peaks (that when there'd be 5+ peaks)
nothing to worry about

[Graphite]

Yes, add them. In theory, if you have a quaternary carbon with all hydrogen environments different, you don't simply multiply 2 environments. Multiplicity doesn't go as after as having a linear chain with a maximum number of 2 hydrogen environments on each side.

[Mao]

Yes, add them. In theory, if you have a quaternary carbon with all hydrogen environments different, you don't simply multiply 2 environments. Multiplicity doesn't go as after as having a linear chain with a maximum number of 2 hydrogen environments on each side.

did you mean tertiary carbon? =)

[Graphite]

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

[Mao]

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.