[Sheekle]

"The reaction mixture was cooled to about 10 °C with an external ice bath, and acidified to a pH of about 3.0 by the dropwise addition of 2.5 N H2SO4. "

How would one acidify a chemical with 2.5 N H2SO4

[gvic]

I would assume that you would simply add the H2SO4 dropwise into the solution until the pH reaced 3.0. You can determine when the pH has been lowered sufficiently with a pH meter or a litmus paper

[Sheekle]

I would assume that you would simply add the H2SO4 dropwise into the solution until the pH reaced 3.0. You can determine when the pH has been lowered sufficiently with a pH meter or a litmus paper

Hmm, sounds reasonable. I'm a huge newb to organic chem so I'm still sorta confused as to how one would measure 2.5 N H2SO4

[Doc Oc]

You can make a molar solution of any acid.  Unless concentration is extremely important to your reaction, you could probably acidify with 1M HCl (I believe this is MUCH more common as a stock solution).

[AC Prabakar]

Hmm, sounds reasonable. I'm a huge newb to organic chem so I'm still sorta confused as to how one would measure 2.5 N H2SO4

I couldn't understand your English!!!!Pls use proper one...
U can get get lot of information regarding preparation/measuring of  2.5 H2SO4(by titrating with suitable base) from google..

[Borek]

I couldn't understand your English!!!!Pls use proper one... U can

In general you are right - using this kind of language is against forum rules. But you are guilty as well.

[Finkelstein]

The N is for "normality."  It refers to the concentration of the H+ ions in the solution.  Because H2SO4 is diprotic (has two hydrogen atoms), you would use a 1.25 M (molarity) solution.

Just taking a wild guess but if you're reading this from TIHKAL, you're gonna need a lot more knowledge on the subject before you can properly do what you're going for.  If you dont know what normality is you have a long ways to go..