random questions

[lzxnl]

At equivalence point in a titration between sodium hydroxide, a strong base, and ethanoic acid, a weak acid, you have effectively only ethanoate ions, which are basic. Therefore, the pH at equivalence point should be above 7 (clearly I don't read graphs very well and have to come up with my own ). Methyl red, as swagsxcboi has pointed out, changes colour in acid conditions, so the volume of the added solution will be calculated to be too large. HOWEVER, remember you're titrating with something of unknown concentration against a base solution of known concentration and presumably volume. No matter what volume you get, the number of moles of hydroxide is the same, and consequently the number of moles of ethanoic acid the student uses for the calculation must remain the same (assuming they do it correctly). As a result, the volume has increased, but the calculated number of moles hasn't, producing a lower calculated concentration.

[hyunah]

hello...
i was wondering can some one please help me too?

So the question says:
suggest why it was necessary to mix vegetable oil (WVO) sample with 2-propanol before the titration
was conducted.
and the ans is:
The non-polar WVO will dissolve in the 2-propanol which will then allow the
NaOH solution to mix and react with the free fatty acids
but if WVO is non polar is it meant to dissolve in the polar propanol in the first place.

thank you very much

[jgoudie]

an issue some students seem to have is that we should not deal with flat out "non-polar" and "polar" but should look at varying degrees of polarity.

WVO is mostly non-polar and 2-propanol is in the middle grounds of polarity, it has will dissolve both polar and non-polar substances (and by the looks of it some ionic substances too).

hello...
i was wondering can some one please help me too?

So the question says:
suggest why it was necessary to mix vegetable oil (WVO) sample with 2-propanol before the titration
was conducted.
and the ans is:
The non-polar WVO will dissolve in the 2-propanol which will then allow the
NaOH solution to mix and react with the free fatty acids
but if WVO is non polar is it meant to dissolve in the polar propanol in the first place.

thank you very much

[Bestie]

um.. why is that the OH doesn't cause splitting in NMR, like there is always only one peak?

Thank you

[lzxnl]

The thing about OH groups is that they are acidic. Sure, they're not very acidic, but they nonetheless are acidic. What happens is that these hydrogens can undergo quick exchange with each other; two ethanol CH3CH2OH hydrogens may swap places, for instance. Peak splitting has to do with the spin of one hydrogen interfering with the magnetic field felt by a hydrogen on a neighboring atom. If the hydrogens are constantly swapped, their spins may also be swapped, so on average, half the time you have a spin up hydrogen, half the time you have a spin down hydrogen, so on average the hydrogen is like it has no spin. Now, this exchange occurs too fast for the NMR machine, so you only see an average, which is no splitting.

[Bestie]

Thank you once again!!! Thank you thank you

I was wondering if you have time could anyone please help me out with these questions.

Thank you

[hyunah]

im sorry for posting on someone else's thread, but...

whats the difference between amine and amino, how can i tell when to use between the two (for eg. when asked for the functional group in the bases of DNA, is it amine functional group or amino functional group)?