How can I find the amount of moles are in 25.0 grams of potassium?

Question

Thanks for your help!

Answer 1

The number of moles in a sample can be found by dividing the mass of the sample by its molar mass.

Molar mass = mass / number of moles
Number of moles = mass / molar mass

The question tells you that the mass of the same of 25.0 grams of Potassium metal.
The molar mass of Potassium is 39.10 g/mol.

Number of moles = (25.0 g) / (39.10 g/mol)
Number of moles = .639 moles of K
In 25.0 grams of Potassium, there are .639 moles of Potassium.

Answer 2

25gK x 1mole/39.1gK = .639 moles of K [potassium]