A mole is a basic unit of measurement in chemistry. One mole of any substance equals 6.02214 * 10^23 particles of that substance. A mole also equals the atomic weight or molar mass of a substance, expressed in grams. A micromole is one mole divided by 1,000,000, which can also be expressed as 1 * 10^-6. Converting from micrograms to micromoles involves using the molar mass of each element in a compound. Molar mass can be found on the periodic table at the bottom of each elemental box.
Convert 2.5 x 10^-5 micrograms of KMnO4 to micromoles. Divide the micrograms by 1 x 10^-6 to put it into gram form: (2.5 * 10^-5) / (1 * 10^-6) = 25.0 grams KMnO4.
Calculate the molar mass of the compound by finding the molecular weight of each element on the periodic table and adding them together: 39.0983 + 54.938045 + (4 * 15.9994) = 158.034 grams/mole (rounded.) Note that the weight for oxygen is multiplied because of its subscript in the chemical formula.
Find the moles by dividing the grams of the compound by the molar mass: 25.0 grams / (158.034 grams/mole) = 0.158 moles KMnO4 (rounded.)
Multiply the number of moles by 1 * 10^-6 to calculate the micromoles: 0.158 * (1 * 10^-6) = 1.58 * 10^-7 micromoles KMnO4.