Step-by-step explanation:
Number of molecules: 4.30×10²⁵
We need to find out the total number of moles.
Now, as per Avogadro's law, 6.02×10²³ of anything (Avogadro's number) constitutes a unit called one mole. Just like 12 is a dozen, 6.02×10²³ is a mole.
If you were given 24 bananas and you had to find out the number of dozens, you would divide the total number of bananas (24) by the number of bananas in one dozen (12).
We do exactly the same here: divide the total number of molecules (4.30×10²⁵) by the number of molecules in one mole (6.02×10²³) to get the number of moles.
4.30×10²⁵ / 6.02×10²³ = number of moles
Solving, we get number of NH3 moles = 71.4 which is your final answer!
Hope this helps :D