J.R. S. answered 05/12/22
Ph.D. University Professor with 10+ years Tutoring Experience
Molar mass KMnO4 = 158 g / mole
0.25 M = 0.25 moles / L
0.25 mol / L x 3 L = 0.75 moles required
0.75 moles x 158 g / mol = 118.5 g = 119 g KMnO4 required (3 sig. figs.)