[groverdot]

I'm doing a first year chem lab: "Chemical Detective" The procedure is as follows:

"Students will perform a semi-quantitative analysis of one of four solutions, each said to have a concentrations of "10" (arbitrary units). Take from the stock solutions, which corresponds to the unknown solution issued. Using that sample of stock solution, some distilled water, and your ingenuity determine an approximate concentration of the unknown solution issued."

So basically I took the solution issued, which was a lighter green solution of about 5.3 mL. I then took 2.0 mL of some stock, which was a darker green. After diluting it with 8.0mL of water, the stock turned the exact same shade of green as the solution issued. Great.How do I determine a concentration of the issued solution from this evidence??

[Borek]

Aren't you told what is the concentration of stock in the same arbitrary units?