We perform this calculation using the formula: CiVi-C2Vz. It is used regularly f

Question

We perform this calculation using the formula: CiVi-C2Vz. It is used regularly for calculating dilutions from a given stock solution. C1 Concentration of stock solution · Vi = Volume of stock solution .C2-Final concentration of new solution .V2- Final volume of new solution Let's say we have 50,000 bacteria/mL in a stock solution of 10mL, but now we want to have a :100 dilution in 5mL of dH20. How many mL do we pipet from the original stock solution? Formula: CVi C2V2 Plug values in: (50,000 bac/mL)(V) (5 mL)(500 bac/mL) So V,-[(5 mL)(500 bac/mL)] / (50,000 bac/mL) Answer: The volume from the original concentration to pipet would be 0.05mL or 50uL into 4.95mL of water to get a final volume of 5mL Work with your group on the following problems: 1) There are 1,436,543 bacteria in a stock solution of 10mL. What is the concentration of bacteria per mL in this stock solution. You make a 1:10,000 dilution of the stock solution. What is the final concentration of the new solution (bacteria/per mL) You have a total of 0.7 x 10° bacteria in a stock solution of 20mL. You want to dilute this so you have 0.7x 101 bacteria/mL in 10mL. What volume of the stock solution do you need? How much dH20 will you aliquot the volume into? 2)

Explanation / Answer

1) if 1436543 cells are present in 10 ml then in 1ml 143654.3 cells are present.

A 1:10000 dilution would mean 14.36543 cells/ml

2) 0.7x106 *X=0.7x103 *10,000ul

So X becomes 10ulthat is you take 10 microlitres of 20ml stock solution and add 9990 microlitres of distilled water in it.

3) 490,000 cells in 1:100 dilution, to make 1:10000 dilution divide the number of cells by 100 and not 10,000 as we are diluting a 100 diluted cell to a final 10,000 which requires dilution by factor of only 100. Therefore 4900 cells will be present in 1:10000 dilution.

4) 44,000cells/ml * 2ml = X * 10ml, Why 10? 8ml is dH2O and 2 ml is stock solution making total volume 5o be 10ml

X becomes 8800 cells/ml

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