Achemist who is performing this reaction starts with 160.1 g of nh4no3. the molar mass of nh4no3 is 80.03 g/mol; the molar mass of water (h2o) is 18.01 g/mol. what mass, in grams, of h2o is produced?

The answer
the general equation of the reaction is 
NH4NO3 N2O   +  2H2O 

The molar mass of NH4NO3 is 80.03 
The mass of NH4NO3 is 160.1 g
 so we can deduce that  

nNH4NO3 = number of mole of NH4NO3 = 160.1 g / 80.03  =2 moles
by using proportion property 

NH4NO3 N2O   +  2H2O 
1mole                       1mole     2 moles
nNH4NO3                                nH2O

the number of mole nH2O can be found by 

1/ nNH4NO3   =  2 /            nH2O 

           nH2O = 2 x  nNH4NO3 = 2 x 2 = 4 moles
to find the mass, we use 

mH2O = 4 moles x  18.01 g /mol = 36 g

Calcium=Ca=Atomic number 20 9+11=20