Answer:
1.16x10^–3 mole
Explanation:
From Avogadro's hypothesis, we understood that 1 mole of any substance contains 6.02x10^23 formula units. This implies that 1 mole of MgBr2 also contains 6.02x10^23 formula units.
Now, if 1 mole of MgBr2 contains 6.02x10^23 formula units,
Then Xmol of MgBr2 will contain 6.99x10^20 formula units i.e
Xmol of MgBr2 = 6.99x10^20/6.02x10^23
Xmol of MgBr2 = 1.16x10^–3 mole
