Hey there!:
Molar mass KMnO4 = 158.0339 g/mol
Number of moles :
n = m / mm
n = 4.0000 / 158.0339 => 0.0253 moles of KMnO4
Volume of solution = 1 liter
Therefore:
Molarity = n / V ( L )
Molarity = 0.0253 / 1
Molarity = 0.0253 M
Hope that helps!
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