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# w/v calculation

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### #1 heathenbrewing

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Posted 27 March 2018 - 07:01 PM

I apologize if this is a elementary question as I do not have a background in science, only seeking to increase my understanding of the discipline.

A media recipe calls for 0.04 g/L CaCl2 2H2O. In order to minimize variance from liter to liter I would favor creating a stock solution as opposed to weighing the dry component for each L made. My goal being the addition of 1mL of the concentrate to 999mL of the media would result in the desired concentration.

If I am understanding the mathematics correctly I should create a 1000X CaCl2 2H2O solution by adding 40g/L. Wikipedia claims this concentration of dihydrate should be soluble in ddH2O.

1mL of 40g/L divided by 1000 = 0.04g/L. Is that correct? If not, where did I error?

### #2 bob1

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Posted 28 March 2018 - 06:02 AM

The equation you want is:

C1V1 = C2V2

Where C1 and V1 are your starting concentrations and C2 and V2 are your final concentrations.

C1 = 40 g/L, V1 = ?, C2 = 0.04 g/L, V2 = 1 L

rearrange to get V1 by itself 0.04*1/40 = 0.001 L or 1 ml.

### #3 heathenbrewing

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Posted 05 April 2018 - 04:31 PM

Thank you for response. I will learn more of the C1V1 calculations but your explanation makes it pretty clear.