Question

Using the total volume at endpoint (51.98mL) and the fact that the concentration of CrO4 ^2- due to Mohr's indicator is 0.26 M, find the actual concentration of CrO4^ 2- at the endpoint (or at the instant just before Ag2CrO4 begins to form).

Any help I am completely lost with this one

Answer 1

How much chromate did you use? If you used, for example, 2 mL, then the concn chromate will be 0.26 x 2 mL/52 mL = ??

Answer 2

the only chromate used was the amount present in 1mL of Mohr's indicator. Does it matter if no addition chromate was added?

Answer 3

There is no need to add more chromate than that in the procedure you're followinig. In that case [CrO4^2-] = 0.26M x (1/52) = ?M.(51.98 instead of 52 if you want to split hairs.) Most procedures that I've seen try to keep [CrO4^2-] somewhere between 0.005 and 0.01M.

Answer 4

thanks