I don't really understand this stoichiometry problem. I can calculate it, but I don't understand it.

Determine the molarity of a solution of potassium dichromate, if it took 50.00mL of 0.1000 M NaCl to completely react with 50.00 mL of the dichromate solution.

14H+ + Cr2O7(2-) + 6Cl- ---> 3Cl2 + 2Cr(3+) + 7H2O

So I know you use MV=M2V2 so .1M *.05mL/.05mL * 1/6 = .0166M

Why do you use 1/6 in the above equation? Why not 6/1 or why not a coefficient from the opposite side?

Can you please explain why you use two coefficients from one side and in the 1/6 order?

I think what you are failing to realize is that the equation tells you how many parts of one reacts with how many parts of the other.

In the equation it says that for every 1 mol of Cr2O7(2-) you will need to use 6 mol of Cl-,

OR looking at it the other way, for every 6 mol of Cl- you will only need 1/6 mol of Cr2O7(2-).

So in your question, you state that you had 50 mL of a 0.1000 mol/L solution of Cl-, That equals to this many mols. 50 mL x 0.100 mol/L = 5.0 millimols of Cl- you had available.

the dichromate however, only requires 1/6 of that to react completely, so 5 x 1/6 = 0.8333 mmol reacts.

Now that you have both the vol and the mol of dichromate you can calculate concentration

C = n / V 0.8333 mmol / 50 mL = 0.0167 mol/L

Did that help? It is all in the mole ratio between the two substances you are interested in.

it is rather simple, base for solution is free chlorine atom, in reaction you supply 6 chlorine atoms (they do not exist in that state, but for purpose of equation we need to consider as there is 6 mole volume of chlorine), but molar solution will get only and only single atom, therefore you are considering 1/6 of available molar volume of chlorine