The molarity of the potassium dichromate is a result of two sequential dilutions. Re- member that you can obtain the dilution factor from the volumes in the dilutions, V2/V1.
To obtain a 0.00650 M K2Cr2O7 solution, a researcher started with 10.0 ml of a concen- trated K2Cr2O7 solution and mixed it with 40.0 ml of deionized water. Then he diluted the obtained solution by a factor of 5. Calculate the molarity of the original concentrated K2Cr2O7 solution used by the researcher.