Answer:
12.91 moles of Mg₂, 8.4x10²⁴ atoms of I.
Explanation:
The number of molecules of any chemical substance is converted to moles using Avogadro's number (That is 6.022x10²³ molecules / mol) :
7.777x10²⁴ molecules * (1mol / 6.022x10²³molecules) =
12.91 moles of Mg₂
As you can see, there are 4 significant figures in the number of molecules and the answer of moles.
In the same way, 14 moles of I are:
14 moles I * (6.022x10²³ atoms / mol) =
8.4x10²⁴ atoms of I
