Question

How do you get molar mass?

Answer 1

You should know the molar mass of each chemical element in the compound. M(el)
Then you should count how many times each element appears in the compound. N
Multiply M(el) by N respectively M₁*N₁, M₂N₂, M₃N₃ for each element and then add these numbers.

For example:
KMnO₄
M(K) = 39 g/mol, M(Mn) = 55 g/mol, M(O) = 16 g/mol.
There are four atoms of the Oxigen in this compound, thus
M(KMnO₄) = 1* 39 + 1 * 55 + 4 * 16 = 158 g/mol.