Answer:
0.069 mol
Step-by-step explanation:
To calculate the number of moles of Mg present in 2.5 x 10^25 atoms of Mg, we can use the following steps:
1. Calculate the number of moles of Mg atoms.
2. Divide the number of moles of Mg atoms by Avogadro's number to get the number of moles of Mg.
**Step 1: Calculate the number of moles of Mg atoms.**
```
Moles of Mg atoms = Number of Mg atoms / Avogadro's number
```
Avogadro's number is 6.022 x 10^23 atoms/mol.
```
Moles of Mg atoms = 2.5 x 10^25 atoms / 6.022 x 10^23 atoms/mol = 4.16 mol
```
**Step 2: Divide the number of moles of Mg atoms by Avogadro's number to get the number of moles of Mg.**
```
Moles of Mg = Moles of Mg atoms / Avogadro's number
```
```
Moles of Mg = 4.16 mol / 6.022 x 10^23 atoms/mol = 0.069 mol
```
Therefore, there are **0.069 mol** of Mg present in 2.5 x 10^25 atoms of Mg.
Answer: 0.069 mol