If I have 40mg of potassium, that would be how many moles of potassium?

Question

mols= grams/atomic number

0.04g/39.0983= .001023062
would equal 1.02 x 10^-3 correct?
Did I do this problem correctly?

Answer 1

Yes it is done correctly but if you have 40 mg that is only two sig figures (and then only if it is written as 40.); therefore, you would be allowed only two in the final answer. You have 3 s.f. in 1.02E-3.