Friday
May 6, 2016

# Homework Help: chemistry

Posted by Anonymous on Monday, February 4, 2008 at 6:50am.

(3 pts) The stockroom prepared a solution by dissolving 0.2300 g of Erythrosin B (MW = 879.87 g/mol) in DI water in a 250.00 mL volumetric flask. A student pipetted 5 mL of the stockroom solution into a 100.00 mL volumetric flask and diluted it to the mark with DI water. The molar concentration of the stockroom's solution in the 250.00 mL flask is
.00105M.
The molar concentration of the student's diluted solution in the 100.00 mL flask is ____M

If the student wishes to prepare 100.00 mL of a 4.50x10^-4M solution, she will need ____mL of the stockroom solution.
• chemistry - bobpursley, Monday, February 4, 2008 at 10:21am

Hmmm.

You are given the Molarity of the stockroom solution. It is diluted by a factor of 20.

Molarity=Mstockroom/20

Now, for the second part

4.6E-4=Mstockroom/dilution factor
solve for dilution factor. Then, amount is equal to 100ml/dilution factor.

There are other ways of doing this. I will be happy to critique your work on the method you were taught.