Question

calculate the volume and mass and number of molecules of hydrogen liberated when 230 grams of sodium reacts with excess water at stp.

Answer 1

2 Na + 2 H2O ===>  2 Na OH + H2

sodium atomic weight = 23 u                hydrogen molecular weight 2 u

so 46 gms of sodium will produce  1 mole = 2 gms of hydrogen.
  230 gms of  sodium  =>    10 gms  =>  5 moles  

 At STP,   5 moles contains = 5 * avogadro number 
                                           = 5 * 6.022 * 10^23    molecules