Question

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

Answer 1

See explanation.

Explanation:

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.