Abalanced chemical equation used to prepare ammonium carbonate, (nh4)2co3 , is: 2 n h 3 ( g ) + c o 2 ( g ) + h 2 o ( l ) ⟶ ( n h 4 ) 2 c o 3 which choice of reactant quantities shown below would result in the greatest amount of ammonium carbonate being formed?

This a simple stoichiometry problem using the ideal gas law.  

First take the grams of ammonium carbonate and convert it to moles using its molar mass and dividing. 11.9 g/96.0932 g/mol= .12384 mol  

Now use a molar conversion using the balanced equation,  

1 mol (NH4)2CO3 ---> 4 mol gas formed (2 mol NH3 + 1 mol CO2 + 1 mol H2O) = .12384 x 4 = .49535 mol gas  

PV=nRT  

V=nRT/P= .49535mol (.08206 Lxatm/molxK) (296K)/ (1.03 atm)=11.682 L

56 moles of   lieter in chemistry