In effect of concentration on rate, why is it important to
havethe same potassiumin four reaction mixtures?

Explanation:

If we change the concentration of Potassium since we take KI solution, concentration of I- changes, then the rate changes accordingly

Rate = k[H2O2 ]^a[I-]^b [H+]^c

The concentrations of I- and H+ are held constant in the procedure

thus to study the rate of the reaction, concentration of KI solution has to be constant only the peroxide solution varies.

solute : a solute is a substance that is dissolved in another substance is known as a solvent. it is mixed with a special mixture know as homogeneous mixture.

solvent: a solvent is a substance that dissolved a solute, which results in a solution is known as solvent.