What is the concentration of 50mL of 0.2M potassium permanganate?
The concentration of 0.2 M potassium permanganate is 0.2 molar; it doesn’t matter how much of it you have, the concentration is the same. Of course, the AMOUNT of potassium permanganate that you have is dictated by the volume that you sampled: 50 ml * 0.2 mole KMmO4/1000ml = 0.01 moles KMnO4 if you had taken 100ml you would have doubled the number of moles of KMnO4 you had taken, but the concentration would still remain the same.
