Concentrations/Dilutions Help

[el123]

Concentrations/Dilutions Help

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Post by el123 » Mon Apr 12, 2010 9:19 am

Hey guys,
I am doing some revision for my cell bio class.

I Can't get my head around dilutions.

I have a question that goes

If you add 15 micro liters of a 10mM solution of glucose to 100mL water, what is the molarity of the solution.

Can some one please explain how I go about doing questions like these?

I know molarity is Moles of solute/Litres of solution. But i am confused which is which? Can someone please take me through how to approach questions like these?

[JackBean]

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Post by JackBean » Mon Apr 12, 2010 9:24 am

Are you sure about the units?

You add 15 ul to 100 ml, that is, you dilute it ~6666.6 times (100ml/15ul), so the concentration will be ~6666.6 times smaller

In this case, you can neglect the volume of added glucose, as it is only 15 ul vs. 100 ml

[el123]

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Post by el123 » Mon Apr 12, 2010 9:31 am

thats the right measurements. but im not sure thats the right answer , something seems off

[jwalin]

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Post by jwalin » Mon Apr 12, 2010 1:03 pm

its right

[JackBean]

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Post by JackBean » Mon Apr 12, 2010 1:16 pm

what is right?

[jwalin]

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Post by jwalin » Mon Apr 12, 2010 4:29 pm

your answer...
although ignoring the 15 microlitre does make a difference but the difference aint too significant so you can ignore it (as you mentiones)