2. Ethanol is supplied in a 90% solution. You need 275 mL of 75% Ethanol for you

Question

2. Ethanol is supplied in a 90% solution. You need 275 mL of 75% Ethanol for your experiment. How would you make this solution?

3.You have 12 mL of cells you need to treat with Hydrogen Peroxide (H2O2), such that the final concentration of H2O2 is 50 uM. How much of a 30 mM stock solution of H2O2 would you add to your cells?

4. You need to prepare a stock solution of medium for your culture cells, which usually includes liquid salt solution and bovine serum. Your liquid salt solution is supplied in a 50X concentration, and you need to dilute it to 1X for use. You also need to add 75% fetal bovine serum for a final concentration of 15%. How would you make up 0.80 liters of this culture media using water as your solvent?

5. You need to treat cells with arsenite such that it has a final concentration of 25 uM once it has been added to the cells. You need to treat 10mL of cells, and you don't want your treatment volume to be more than 7 uL per 1mL of cells. What concentration should you make your stock solution?

Explanation / Answer

1.

250*10^-6 = (x/110.99)*(1000/750)

250*10^-6 = 4x/(110.00*3)

0.0189 g/ ml

2. C1V1 =C2V2

C1   = 90%, C2 = 75%, V2 = 275 ml, V1 = ?

from formula,

90% * V1 = 75 % * 275 ml

V1    = 229.16 ml

take 229.16 ml of 90% ethanol add 45.84 ml distilled water to it. this will be 275 ml of 75% ethanol.

3.

Calculate the final concentration of H2O2:

N1V1=N2V2

50uM*12 mL = 30mM*?

Note: convert the milli molar to micro molar

1 milli = 1,000 micro

So, the above equation should be converted to

50uM*12 mL= 30*1000*?

600=30000*N2

N2=600/30000

N2=0.02 mM

0.02 mM solution should be added to cells.

4. Apply the formula, C1 * V1 = C2 * V2, twice.

For the salt solution, C1 = 50, V1 = unknown (L), C2 = 1, V2 = 0.80 (L)
50 * V1 = 1 * 0.80
Therefore, V1 = 0.016 L

For the FBS, C1 = 75 (%), V1 = unknown (L), C2 = 15 (%), V2 = 0.80 (L)
75 * V1 = 15 * 0.80
Therefore, V1 = 0.16 L

Volume of water required = 0.80 - 0.16 - 0.16 = 0.48 L.

Thus, use 0.16 L of salt solution + 0.16 L of FBS and add 0.48 L of water,
to make 0.80 L containing 1x salt solution and 75% FBS.

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