For the reaction of 2Na20, if you have 18.0 g of Na, how many grams of O2 are needed for reaction?

6.26 g of O2.

Explanation:

We'll begin by writing the balanced equation for the reaction of sodium, Na and oxygen, O2 to produce sodium oxide, Na2O.

This is shown below:

4Na + O2 → 2Na2O

Next, we shall determine the masses of Na and O2 that reacted from the balanced equation.

This is illustrated below:

Molar mass of Na = 23 g/mol

Mass of Na from the balanced equation = 4 x 23 = 92 g

Molar mass of O2 = 16x2 = 32 g/mol

Mass of O2 from the balanced equation = 1 x 32 = 32 g.

From the balanced equation above,

92 g of Na reacted with 32 g of O2.

Finally, we shall determine the mass of O2 needed to react with 18 g of Na.

This can be obtain as follow:

From the balanced equation above,

92 g of Na reacted with 32 g of O2.

18 g of Na will react with = (18 x32)/92 = 6.26 g of O2.

Therefore, 6.26 g of O2 is needed for the reaction.