-calculez moli NH3 ,stiind M,NH3= 17g/mol
niu=m/M=340g/17g/mol= 20mol
-deduc moli si masa N2,H2, din ecuatia
1mol......3mol.......2mol
N2 + 3H2---> 2NH3
x...........y...............20mol
x=10mol y= 30mol
M,N2= 28g/mol----> m=niuxM= 10X28=> 280gN2
M,H2=2g/mol------> m,=30x2=> 60gH2