Hi,
I am having trouble with some questions on my lab:

1. The composition of TE buffer is 10mM Tris-Cl, 1mM EDTA. You are given a stock solution of 1M Tris-Hcl and a stock solution of 500 mM EDTA and you are asked to make 100mL of TE buffer. How many mL of each stock solution will you need?

And

2. You want to prepare Luria Broth (LB)/ampicillin plates. The final ampicillin concentration in the media is to be 100micrograms/mL. You first make up 1L of LB media and 10mL of a 100mg/mL ampicillin stock solution. How many mL of this stock solution will you add to the LB media to bring the final ampicillin concentration to 100 micrograms/mL?

And

3. You just make up 1L of Luria broth media. The Luria broth still needs ampicillin to be added to a final concentration of 50micrograms/mL. How much of a 5 mg/mL solution of ampicillin should you add to the media?

If you can help explain the answer to any or all of these, THANK YOU!!

1. I suppose mM means milli molar?

In 1 L of TE, you have 10 mmol Tris-Cl and 1 mmol EDTA.

So, in 100 mL of TE, you will have 1 mmol Tris-Cl and 0.1 mmol EDTA, which is 0.001 mol Tris-Cl and 0.0001 mol EDTA.


In 1 L of solution of Tris-Cl, you have 1 mol solute.

1 mol -> 1 L
0.001 mol -> ? L

In 1 L of solution of EDTA, you have 500 mmol solute, or 0.5 mol.

0.5 mol -> 1 L
0.0001 mol -> ? L

Convert to mL.

Can you try out the rest by yourself and post what you get?