Question

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  step:  calculate  the  number  of  moles  of   sodium  reacted
moles=mass/molar  mass
     31.5g/23g/mol =1.37moles
from  the  reaction  above  the  reacting  ratio  of  Na  to  H2  is   2:1  therefore  moles  of  H2  is 1.37/2=0.685
At  STP   1  mole  = 22.4L what    about  0.685  moles
22.4  x0.685=15.344L