extinction coefficient

[pinkypig]

how do you calculate an extinction coefficient?

[Preccious]

Extinction Coef ( e) can be calculated by Lambert Beer Formula:

Abs = e * b * c

Abs : is the absorbance ;

b : is the path length of the cuvette in which the sample is contained, usually in cm, and the most common value is 1cm

and

c is the concentration of the compound in solution.

[pinkypig]

thanks alot for that!but don't you use the gradient of the graph you plot of absorbance and concentration?or is that a more difficult way of doing it?

[Preccious]

both are correct, you must use the one more indicated to each situation.
Depending on the data you have, you chose.

[pinkypig]

oh rite, well we've been told to calculate it using a graph we drew but i don't know how to do it that way,could you help please?

[pinkypig]

Also can you explain to me how to calculate pKa?or do i need to make another post for that too?lol

[Preccious]

oh rite, well we've been told to calculate it using a graph we drew but i don't know how to do it that way,could you help please?

do you have a graph abs X concentration, you use te points to make a trend line Y=mX+b

the E you are seaching is the m, the slope.

Check this example, I guess it will help :

http://icn2.umeche.maine.edu/newnav/New ... e_3614.htm

[Preccious]

Also can you explain to me how to calculate pKa?or do i need to make another post for that too?lol

Do you have the Ka?

[pinkypig]

emm what is the Ka?i probably do have it but just don't know what it is,

[Preccious]

emm what is the Ka?i probably do have it but just don't know what it is,

erm.. tha is really basic..

what kind of work are you doing?

that is explained in any chemistry book.

you can see something here: http://www.chemsilico.com/CS_prpKa/PKAintro.html

Good Luck

[pinkypig]

That is very helpful but where it says Ka= all the H and X stuff what does that stand for??

[mith]

The Ka gives you the amount of ions formed.