Salut!
A) n=N/NA
n=nr de moli
N=nr de molecule
NA=nr lui Avogadro
n=(48,176•10^26)/6,022•10^23
n=8•10^3 moli
n=8000 de moli
B)2,4kg de pirita=2400 grame
55+32•2.....2400
32•2......X ( S=32,Fe=55 masele molare)
X=(2400•64)/119=1290,75 grame de S in FeS2
Acum 2•1+32.....Y
32....1290,75
Y=(34•1290,75)/32=1371,42 grame de H2S
C)n=m/masa molara
masa molara=m/n
masa molara=81,6/2,4=34 g/mol