Post by: andrewloppol on May 28, 2010, 04:44:41 pm
Post by: fady_22 on May 28, 2010, 07:32:24 pm
Post by: stonecold on May 28, 2010, 07:36:01 pm
Yep, you can put proteins through electrophoresis, but you must put them in either an acidic or basic solution to give them a charge so that they can migrate to the pole with opposite charge during electrophoresis.
Yeah, this was on STAV 08. Good question. :)
Post by: Martoman on May 28, 2010, 08:08:58 pm
Post by: kenhung123 on May 28, 2010, 08:11:51 pm
Yep, you can put proteins through electrophoresis, but you must put them in either an acidic or basic solution to give them a charge so that they can migrate to the pole with opposite charge during electrophoresis.Can it be any charge or must be negative? If its positive how can it migrate to positive electrode?
Post by: Martoman on May 28, 2010, 08:15:15 pm
It can be any charge.
Post by: stonecold on May 28, 2010, 08:18:15 pm
There were people who said they laughed when TSFX said in one of their exams that the oxidation number of nitrogen was 1/3.
Post by: kenhung123 on May 28, 2010, 08:19:37 pm
Post by: stonecold on May 28, 2010, 08:20:52 pm
Post by: Martoman on May 28, 2010, 08:30:22 pm
Post by: Martoman on May 28, 2010, 09:35:41 pm
2-methylpropanol + 2-methylpropanoic acid ----(conc. H2SO4)---> XXXXXX
Is it soluble or insoluble in water? I said insoluble, solutions to chemology 2010 say soluble though.. why :P?
I don't know why they would say this. It is sufficiently big to mean that it is relatively insoluble.
Post by: kenhung123 on May 28, 2010, 09:41:16 pm
Post by: fady_22 on May 28, 2010, 10:26:28 pm
And there's really nothing hydrophillic about it? The (=O) only?
Yes, but don't forget the side groups. These make the molecules harder to pack close together, and so the relative strength of the dispersion forces are low. Hence, probably soluble.
Post by: fady_22 on May 28, 2010, 10:29:38 pm
Post by: Mao on May 29, 2010, 02:04:23 am
Since you've all got one - I'll post my Q's here:
Cr2O2-... oxidation number of Chromium here and why? Solution says +3.
It is as Martoman has said, 3/2. Oxidation numbers don't have to be whole numbers.
Quote
2-methylpropanol + 2-methylpropanoic acid ----(conc. H2SO4)---> XXXXXX
Is it soluble or insoluble in water? I said insoluble, solutions to chemology 2010 say soluble though.. why :P?
I would also say it's insoluble (or poorly soluble). The resulting ester is has 8 carbons with an ester bond. Solubility is poor with C5 esters, let alone C8. Bad question imo.
Post by: Martoman on May 29, 2010, 12:30:53 pm
Post by: fady_22 on May 29, 2010, 06:41:54 pm
Maltose is a disaccharide with two glucose molecules.QuoteMaltose is a dissacharide like sucrose. Sucrose is shown in the data book. Counting the
hydroxyl groups gives 8 and there are 3 ether groups counting the two in the rings themselves.
I thought only one ether :S??
Each glucose molecule contains one ether group in the ring itself, and the link between the two glucose molecules is also an ether. In total, 3 ether groups.
Post by: m@tty on May 31, 2010, 10:27:46 pm
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Isn't that the lazy man's structural formula? I always thought that structural required all CH bonds to be expanded... In fact all bonds except OH..
But I'm not sure...
Post by: kyzoo on May 31, 2010, 10:51:32 pm
Semi-structural formula is any shortcut method, such as CH3CH2OH.
Post by: Mao on June 01, 2010, 02:47:37 am
Basic questions, but:
With IR spec, is it the bonds or the entire molecules absorbing the infra-red radiation that cause it to vibrate, stretch etc.?
****
It's individual bonds that absorb.
**
Incorrect. Both absorption occur (bonds and molecule). The molecular absorption occur at lower wavenumbers (fingerprint region), where combination of bonds/structures absorb energy. This is why every molecule have different fingerprint regions.
Post by: kakar0t on June 05, 2010, 06:32:10 pm
9. not sure
Post by: vexx on June 05, 2010, 06:37:22 pm
The equation given is a reduction, so the other has to be an oxidation which is an equation wrote with the 'e' on the right side, from this you can already tell it has to be Fe2+ ---> Fe3+ + e- or else if it were fe3+ it would be reducing.
after that balance the equations, find n(cr2o7 2-), using ratio get mole of iron, then divide the mass given of the salt by the mole, and take away the molar mass of fe, and theres your mass of the other elements.
Post by: Martoman on June 05, 2010, 07:17:39 pm
Like you get the mass of Fe then you subtract it from the mass of whole thing.
Then you need to find empirical formulas that match.
The only one that does is D.