Calculate how to make 10 ml of a 7.5% methylene blue stock solution (from solid

Question

Calculate how to make 10 ml of a 7.5% methylene blue stock solution (from solid powder) Calculate how to make a series of 1:10 dilutions of this stock. Imagine you'll use 5 ml of each dilution for your experiment. Calculate the final concentrations of each tube tube 1: take some stock, dilute it 1:10 with some water in a new tube = #1 tube 2: take some of #1, dilute it 1:10 with some water in a new tube tube 3: take some of #2, dilute it 1:10 with some water in a new tube tube 4: take some of #3, dilute it 1:10 with some water in a new tube First, decide the total volume to make of each tube-keep in mind measurement accuracy (consider preparing 20% more solution than what you will use). Then, calculate how much stock, water and final concentration of each. Then, instead of doing a serial dilution, calculate making each of the above solutions using the weight/volume % solution method. Pros and Cons of serial dilution method vs W/V method

Explanation / Answer

Dear Student,

For 100 ml Methylene blue stock soluttion

7.5 g methylene blue trihydrate (M.W 373.9g) solid powder in distilled water.

so for 10 ml Methylene blue stock soluttion, disslove = 7.5*10/100=0.75 g in 10ml distilled water.

now for tube 1,

1 ml stock solution + 10 ml distilled water= #1

therefore concentration is 0.75%

for tube 2, 1 ml #1 solution + 10 ml distilled water= #2

conc. =0.075%

for tube 3, 1 ml #2 solution + 10 ml distilled water= #3

conc.= 0.0075%

For tube 4 1 ml #3 solution + 10 ml distilled water= #4

conc.=0.00075%

Regards,

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