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Another Calculation Post - HELP PLEASE

Hey Guys

I am really hoping someone could help....
I am a first year pharmacy student but I haven't studied chemistry or maths for about 3 years as I have just completed a degree in Biomedical Science (I got a first from Queen Mary, University of London) and that course did not cover much chemistry or math.

Hence, in pharmacy I fear I will struggle but I am determined to do well.

I have some practice questions and I was hoping you would be able to help and point me in the right direction.

The volume of an organ bath is 25ml, you are given a stock solution of acetylcholine at a concentration of 5 microM and you add 0.4mL of this stoock to the organ bath.

A) What is the dilution factor
25/0.4 = 62.5

B) What is the final concentration, expressed in microM of acetylcholine in the bath?
5microM/ 62.5 = 0.08microM

C) How many moles of acetylcholine are present in the bath?

Am i right in thinking this means
moles = volume * concentration/1000
so it would be...0.08 *25/1000 = 0.002mol or 2mol*10-3

D) If the RMM of acetylcholine is 285, how many nanograms (ng) of acetykcholine are present in the bath?

Would this be...
mass = amount*molar mass
= 0.002 * 285
= 0.57mg *1000 = 570 ng

E) You are given a stock solution of atropine at a concentration of 2microM. What volume of this solution would you need to add to the bath to give a final concentration of 10-8 (10 to the minus 8) M?

F) You are given a stock solution of an unknown drug (RMM = 400) at a concentration of 0.1mg/mL. You then add a 0.2mL volume of this solution to the bath. What is the final concentration of the drug expressed in microM?

I really do hope you can help and advise on any textbooks that would be handy.
:confused: :confused: :confused:

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