Question

30 pts! Sodium and water react according to the following equation. If 31.5g of sodium are added to excess water, how many liters of hydrogen gas are formed at STP? Show all work for credit. 2Na+2H2O--> 2NaOH+H2

Answer 1

First, calculate the number of moles of sodium present with the given mass,

              31.5 g of sodium x (1 mol sodium/ 23 g sodium) = 1.37 mol sodium

It is given in the equation that for every 2mols of sodium, one mol of H2 is produced.

           mols of H2 = (1.37 mols sodium)(1 mol H2/ 2 mols sodium)
                  mols of H2 = 0.685 mols H2

Then, at STP, 1 mol of gas = 22.4 L.
                
                 volume of H2 = (0.685 mols H2)(22.4 L / 1 mol)
                     volume of H2 = 15.34 L

Answer: 15.34 L