Question

How much of a 25mg/ml chloramphenicol stock solution do we need to make 400ml of growth media that has final 25ug/ml concentration of chloramphenicol?

Answer 1

Answer : The volume of chloramphenicol stock solution needed is, 0.4 mL

Explanation :

First we have to calculate the mass of chloramphenicol.

As, the mass of chloramphenicol in 1 mL of solution =
`25\mu g=25* 10^(-6)g`

So, the mass of chloramphenicol in 400 mL of solution =
`(400mL)/(1mL)* 25* 10^(-6)g=0.01g`

Thus, the mass of chloramphenicol is, 0.01 g

Now we have to calculate the volume of chloramphenicol stock solution needed.

Concentration of chloramphenicol =
`25mg/mL=25* 10^(-3)g/mL`

As,
`25* 10^(-3)g` of chloramphenicol needed 1 mL volume of chloramphenicol stock solution

So,
`0.01g` of chloramphenicol needed
`(0.01g)/(25* 10^(-3)g)* 1mL=0.4mL` volume of chloramphenicol stock solution

Thus, the volume of chloramphenicol stock solution needed is, 0.4 mL