Answer
K2CrO4 has the highest concentration of potassium ions.
Work Step by Step
0.20M KCl, 0.15 M K2CrO4 or 0.080M K3PO4
in the 0.20M KCl, for KCl there is 1 mol of K for each mole of KCl so you have 0.20 M K+
in the 0.15 M K2CrO4, there are 2 moles of K for each mole of K2CrO4 so you have 0.30M K+
in the 0.080M K3PO4 there are 3 moles of K for each mole of K3PO4 so you have 0.24M K+
The highest of these is the K2CrO4 at 0.30M
