Calculate the number of moles in the following mass (a) 7.85 g Fe (atomic mass = 56) (b) 4.68 mg of is (at mass 28).

Explanation

(a) 7.85 g Fe
No. of moles = `("mass in g")/("atomic mass")`
No. of moles `=(7.85)/56 = 0.1401`
(b) 4.68 mg of is
No. of moles `=(4.68 xx 10^(-3))/28 = 1.67 xx 10^(-4)`