Number 7 please I’m struggling

One mole of hydrogen has a number of molecules equal to the Avogadro Constant or 6.022* 10^23. 1.06 moles of hydrogen is equal to 6.022* 10^23* 1.06 = 6.38*10^23 molecules. Therefore the number of molecules of hydrogen that 48.7 g of sodium added to water yields is 6.38*10^23.

The balanced chemical reaction is written as:

4Al + 3O2 = 2Al2O3

To determine the mass of oxygen gas that would react with the given amount of aluminum metal, we use the initial amount and relate this amount to the ratio of the substances from the chemical reaction. We do as follows:

moles Al = 16.4 g ( 1 mol / 26.98 g ) = 0.61 mol Al
moles O2 = 0.61 mol Al ( 3 mol O2 / 4 mol Al ) = 0.46 mol O2
mass O2 = 0.46 mol O2 ( 32.0 g / mol ) = 14.59 g O2

Therefore, to completely react 16.4 grams of aluminum metal we need a minimum of 14.59 grams of oxygen gas.