How many grams of sodium will react to make 15.5 g of sodium oxide?

Let’s write the reaction equation:

4Na + O2 = 2Na2O

Let’s find the amount of sodium oxide substance:

v (Na2O) = m (Na2O) / M (Na2O) = 15.5 / 62 = 0.25 (mol).

According to the reaction equation, 2 moles of Na2O are formed from 4 moles of Na, therefore:

v (Na) = v (Na2O) * 4/2 = 0.25 * 4/2 = 0.5 (mol).

Thus, the mass of sodium that has reacted is:

m (Na) = v (Na) * M (Na) = 0.5 * 23 = 11.5 (g).

Answer: 11.5 g.