# The Naked Scientists Forum

#### drkev

• Guest
« on: 11/11/2003 22:37:26 »
Can you please tell me where I am going wrong folks or if I'm right.

Use the calibration curve plotted in Experiment 4.1 to calculate the concentration of PNP (uMolar) responsible for producing each absorbance reading.

y=0.0175x - 0.0014

OK so I am trying to find x. We take the absorbance (which is 0.033) we add 0.0014 to this to get rid of the -.0014 on the right.

We then divide both sides by .0175. This gives us 1.966. Where do I go from here? The original volume used was 5cm3 (where 3 means to the power of 3)

Live long and Love life

Kevin Fisher

#### chris

• Neilep Level Member
• Posts: 5334
• Thanked: 65 times
• The Naked Scientist
« Reply #1 on: 11/11/2003 22:41:08 »
What are the axes ?

chris

"I never forget a face, but in your case I'll make an exception"
- Groucho Marx

#### drkev

• Guest
« Reply #2 on: 11/11/2003 23:06:52 »
x is concentration and y is absorbance

Live long and Love life

Kevin Fisher

#### chris

• Neilep Level Member
• Posts: 5334
• Thanked: 65 times
• The Naked Scientist
« Reply #3 on: 11/11/2003 23:32:00 »
Kev - the equation stated is a straight line, not a curve as the question states - is the function right ?

chris

"I never forget a face, but in your case I'll make an exception"
- Groucho Marx

#### drkev

• Guest
« Reply #4 on: 11/11/2003 23:44:41 »
yes its right

Live long and Love life

Kevin Fisher

#### cuso4

• Angel Delight
• Sr. Member
• Posts: 422
« Reply #5 on: 12/11/2003 08:24:24 »
if the function is right then I don't see any error in your calculation. 1.966 is the concentration.

"Anyone who has never made a mistake has never tried anything new." -Albert Einstein

#### drkev

• Guest
« Reply #6 on: 12/11/2003 17:06:39 »
I was confusing the issue but I have resolved it now I went to sleep and when I woke up I had the answer!!!

There were about 6 different things that had to be worked out and I was confusing them.

But I have sussed it now

Live long and Love life

Kevin Fisher

#### tom

• Jr. Member
• Posts: 22
« Reply #7 on: 13/11/2003 12:10:09 »
quote:
Originally posted by drkev

x is concentration and y is absorbance

Live long and Love life

Kevin Fisher

#### tom

• Jr. Member
• Posts: 22
« Reply #8 on: 13/11/2003 12:15:32 »
This is ordinary Beer-Lambert's law of p-nitrophenol at 402 nm with molar ext. coeff. of ~18300 l/mol.cm. Am I wright?