you ask your lab assistant to prepare IL of solution Zeta at a concentration of 1M. He comes up to you with a 0.5M stock solution ans asks for help in calculating how much to use. what do you tell him?
I dont think my answer is correct. I got 2000 mL of stock solution.
this is how i got my answer.
1) find N-fold: Stock concentration/working concentration = 0.5 M/1M = 0.5, so the n-fold is 0.5.
2) find stock volume: final volume of working solution/ n-fold = 1000mL/0.5n-fold= 2000mL of stock volume.
this answer doesnt make sense though because the final working solution volume should be 1L. can someone help me and tell me what im doing wrong :(
the stock solution is half the concentration of the desired solution
new (more concentrated) solution will have to be made
your calculation shows how to get the one mole of solute that would be in 1L of 1M solution
... the problem is the volume of solution needed at the lower concentration
1M / 0.5M = 2 n-fold dilution
1L = 1000 mL
1000mL / 2 = 500
Use 500 mL volume of stock + 500 mL of water
To calculate the amount of 0.5M stock solution needed to prepare a 1M working solution, you are correct in finding the n-fold, but there seems to be a mistake in the calculation of the stock volume.
Let's go through the steps again:
1) Find the n-fold: Stock concentration/working concentration = 0.5 M/1 M = 0.5. The n-fold is indeed 0.5.
2) Find the stock volume: Final volume of working solution / n-fold = 1 L / 0.5 = 2 L.
So, the correct answer is that your lab assistant needs to use 2 liters of the 0.5M stock solution to prepare 1 liter of the 1M working solution.
It seems like your initial calculation incorrectly assumed the final working solution volume to be 1000 mL instead of 1 liter (1000 mL = 1 L), which led to the incorrect stock volume calculation.
Remember to use consistent units throughout the calculations, and in this case, make sure to use liters for all volumes to avoid confusion.