chem distinguish

Method 1
Separately add a few drops of each solution to a red litmus paper.
Potassium hydroxide solution: turns the red litmus paper to blue.
Potassium nitrate solution: no change on the litmus paper.

Method 2
Add separately copper(II) sulphate solution to each of the two solutions.
Potassium hydroxide solution: A blue precipitate of Cu(OH)2 is formed.
Potassium nitrate solution: no precipitate is formed.