How many moles of aluminum do 5.6×1024 aluminum atoms represent? express your answer using two significant figures?

1 mole of Aluminum = 6.02×10²³ atoms [Avogadro's constant]
1 atom = 1/[6.02×10²³] mole
so 5.6×10^24 atoms = 5.6÷6.02× 10^(24-23)
= 0.93×10¹ = 9.3 moles [ to 2 SF]

The reaction for the production of NO₂ is as follows:

2 NO + O₂ → 2 NO₂

Then, we use stoichiometry to solve the problem. The solution is as follows:

8 molecules NO₂ (1 molecule O₂/2 molecules NO₂)(0.75) = 3

Therefore, it will need 3 molecules of oxygen for a 75% yield.