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# chemistry problem help ?! watch

1. You have reached the maximum response for the drug you are testing but when you plot the data you realise you need a response value for -7.5 on your log [Drug(M)] scale.You have a stock solution of 1µM and the organ bath is 10 ml, what volume (in µl) of this stock will you need to add?

** BTW I DON'T JUST WANT AN ANSWER I NEED TO KNOW HOW TO TACKLE THESE KINDS OF PROBLEMS, SO A STEP BY STEP KIND OF THING WOULD BE GREAT**
many many thanks !
2. -Determine the concentration that gives a response rate of -7.5 from graph
-Use the equation C1V1=C2V2 to determine the volume of stock solution required to prepare a 10mL solution of the concentration determined using graph.

That's the best I can do with the amount of info you've provided. Hope this helps
3. First, unlog the log[drug] value (mostly likely a log10). This gives you the concentration you're looking for in the organ bath, in this case 10^(-7.5)M.
Then, work out how much 1uM solution you need to add to 10ml water to make this concentration.
So (10^(-7.5))/(10^(-6)) = 0.0316..., this is how much you need to dilute the stock to get a concentration of 10^(-7.5)M.
Then, you want to make up this concentration in 10ml water, so times by 10 for an answer of 0.316ml or 316ul.

Is that right?

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Updated: October 27, 2015
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