The Vespiary

The Hive => Chemistry Discourse => Topic started by: Vibrating_Lights on May 10, 2003, 07:33:00 AM

Title: Base Calculations
Post by: Vibrating_Lights on May 10, 2003, 07:33:00 AM

What rules do i use to determine How much sodium carbonate to add to a mix of MeCN:H2O2:MeOH:Alkene to make the Ph 8 for an epoxidation?
VL_ ;)

Title: pH paper is the best method.
Post by: Rhodium on May 11, 2003, 09:15:00 AM

pH paper is the best method.

Title: I'M TRYING TO LEARN HERE
Post by: Vibrating_Lights on May 17, 2003, 08:10:00 AM

Surely there is a way to calculate it before hand.  Whata gives.  I can't even think of where to look for such info.
Vl_

Title: pH calculations are only valid in aqueous...
Post by: Megatherium on May 17, 2003, 08:40:00 AM

pH calculations are only valid in an aqueous medium (i.e. not in a acetonitrile / methanol mix).

Title: pH in non-aqueous protic solutions
Post by: Rhodium on May 17, 2003, 01:21:00 PM

Megatherium: That is not exactly true, you can make valid pH calculations in all protic solvents (such as methanol), not exclusively in water. However, you need to use a completely different set of variables than when doing it for aqueous solutions.

V_L: It's nice that you are trying to learn, but it is incredibly difficult to calculate beforehand what pH an aqueous mixture will have if you are adding several different solutes, as well as aubstances which aren't simple acids and bases. In this case, when it isn't even an aqueous solution, then you are really far out...