Answer:
0.013 moles
Explanation:
To find the number of moles in a substance given it's number of entities we use the formula
[tex]n = \frac{N}{L} \\[/tex]
where n is the number of moles
N is the number of entities
L is the Avogadro's constant which is
6.02 × 10²³ entities
From the question we have
[tex]n = \frac{7.81 \times {10}^{21} }{6.02 \times {10}^{23} } \\ = 0.012973...[/tex]
We have the final answer as
0.013 moles
Hope this helps you
