Răspuns:
p=m pur/m impur*100 => mpur=80×300/100=240g Ca
calculam in grame masa de Ca3N2
3Ca + N2 → Ca3N2
MCa=40g/mol
MCa3N2=3×40+2×14=148g/mol
80g Ca...........................148g Ca3N2
240g0g Ca........................x
x=240×148/80=444gCa3N2
calculam in moli masa de Ca3N2
MCa=40g/mol
m=240g
n=240/80=3moliCa
3moli 1mol
3Ca + N2 → Ca3N2
3moli ymol
y=3×1/3=1molCa3N2
Explicație: