What are the formula, molar mass, and color of potassium permanganate?

Potassium permanganate is the potassium salt of the permanganate anion, #"MnO"_4^(-)#.

Since potassium form #1+# cations and the permanganate anion carries a #1-# charge, you can say that one formula unit of potassium permanganate contains

• one potassium cation, #1 xx "K"^(+)#
• one permanganate anion, #1 xx "MnO"_4^(-)#

Therefore, the chemical formula for potassium permanganate will be #"KMnO"_4#.

The molar mass of potassium permanaganate can be found by adding the molar masses of its constituent elements.

You will thus have

#M_ ("M KMnO"_ 4) = M_ ("M K") + M_ ("M Mn") + 4 xx M_("M O")#

Use the periodic table to write

#M_("M KMnO"_4) = "39.0983 g mol"^(-1) + "54.93085 g mol"^(-1) + 4 xx "15.9994 g mol"^(-1)#

#M_ ("M KMnO"_4) = "158.027 g mol"^(-1)#

Finally, potassium permanganate has a dark gray - bronze - purplish color in the solid state and a magenta color in solution.