You are applying for a lab position. The post-doc asks to you prepare him 100ml

Question

You are applying for a lab position. The post-doc asks to you prepare him 100ml of 1x TAE buffer to demonstrate your buffer preparation technique. He gave you the recipe of Tris-acetate-EDTA (TAE) buffer, and pointed out where to obtain the stock solutions. The largest graduated cylinder you can use in the preparation process, and store the final buffer product, is 1 L. However, due to time consumption issue and limited supplies, you are ONLY allowed to use max of 2 graduate cylinders of any size you choose for each reagent preparation (2 dilutions max for serial dilution). Any volume lower than 1ml is impossible to measure on any graduate cylinder. You are not allowed to use any pipettes in the preparation. Knowing that you are struggling with math, the evil post-doc hinted that to make 1mM EDTA solution, you will need to mix 0.37g of EDTA with 1000ml distillated water. To get full points, please show all works, includes dilution factors.

Recipe for 1X TAE buffer- 40mM Tris pH 7.6, 30mM Acetic Acid, 1mM EDTA solution. Stock Solutions- 10M Tris pH 8.0, Acetic Acid (Molecular Weight= 60.05), 5% EDTA solution

Explanation / Answer

10,000mM * X = 40 mM x 100 ml

X = 4/10 = 0.4 ml

This shows if you make a dilution of 100 factor, you can measure 40 ml of stock solution

i.e.

From 10, 000mM make 100 mM, lets say 1000ml

10,000mM*X= 100mM*1000ml

X= 100*1000/10000= 100 ml

That is take 100 ml of 10M tris and add 900ml water too get 100mM solution

Now, from this make 40mM

100mM*X= 40mM*100ml

X= 4000/100=40 ml

To make acetic acid,

W= 60.05* 30mM*100ml/1000*1000 = 180 mg in 100ml

5% EDTA you have 5 g in 100 ml

first, calculate the molarity you have

5g= M*292.24 g/mol*100ml/1000 (I am assuming here that you 100 ml of 5% EDTA)

0.17 M

Now by C1V1=C2V2 calculate the amount of 5% EDTA you need to make 1mM

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