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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: hunterxv on June 11, 2005, 02:00:44 PM

Title: regarding optic alcohols and pH
Post by: hunterxv on June 11, 2005, 02:00:44 PM

i've been looking for this like hell, and I think I have excluded a few, but I can´t find.

Im supposed to answer what of the following alcohols är optically active, but Im not so sure what it really means.

CH3CH2CH2CH2OH
(CH3)3COH
(CH3)2CHCH2OH
CH3CH(OH)CH2CH3
CH3CH2CH(OH)CH2CH3

also, there's one thing a about pH that i need to calculate. I've got a solution of 0,1M NH4NO3 and I'm supposed to calc pH.
And is Ka(NH4+) = 5,6*10^-10. So It's pKa = -lg 5,6*10^-10 = 9,25, right?

I dont know it from there, am I supposed to calculate with H20 aswell since if says solution? does it NH4 get protolysed so I get NH3 and H3O? since water can act both as a base and acid?

I appreciate all the help I can get, thx!

Title: Re:regarding optic alcohols and pH
Post by: lemonoman on June 11, 2005, 08:43:27 PM

You said you tried.  That's all I have to go on.

Optically active compounds, I once learned, are ones that are chiral...that is, (in organic chemistry) there's a carbon in the chain that has four different substituents.

For example, CH₂Cl₂ is not chiral.  There are two hydrogens.
CHClFI is chiral.  The one carbon has four different substituents.
C(CH₃CH₂CH₂)(CH₃CH₂)(CH₃)(C₆H₅) is chiral as well.  Four different substituents.

Someone else might help out with the pH question...but I would recommend just talking to a teacher or another student or consulting a textbook...just to lay the basics down for you.

Good luck.  :)

P.S. I NEVER learned chriality until second-year university...is it in some highschools?

Title: Re:regarding optic alcohols and pH
Post by: Donaldson Tan on June 11, 2005, 08:46:41 PM

i learned chirality during my pre-university GCE A levels back home.