Answer:
The answer is 0.0042 moles
Step-by-step explanation:
To find the number of moles of a substance given it's number of entities we use the formula
![n = (N)/(L) \\](https://img.qammunity.org/2021/formulas/chemistry/high-school/ak7k0w4ze80j1ablopkgu8j8wur48jz22k.png)
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
N = 2.50 × 10²¹ atoms of silicon
So we have
![n = \frac{2.50 * {10}^(21) }{6.02 * {10}^(23) } \\ = 0.0041528239...](https://img.qammunity.org/2021/formulas/chemistry/high-school/lg1edh93h5g16v42bufjl1i09ghj6va2mk.png)
We have the final answer as
0.0042 moles
Hope this helps you