How much K2Cr2O7 must be added to saturate a solution at 20°C?

[mmmeraki]

Homework Statement

How many grams of K2Cr2O7 (350 g 6,50%) must be added to get saturate the solution at 20C (12,6 g/100 g)?

Homework Equations

The Attempt at a Solution

350 g x 0,065 = 22,75 K2Cr2O7
I got 10 g, but it's not correct. The correct answer is 18,5 g.

 

[Borek]

You calculated the amount of the dichromate already present, not the amount that has to be added to saturate the solution.