a/ 2Al + 3S -to-> Al2S3
b/ Fe + S -to-> FeS
c/ Pb + S -to-> PbS
d/ 2Na + S -to-> Na2S
a/ 2Al + 3S -to-> Al2S3
b/ Fe + S -to-> FeS
c/ Pb + S -to-> PbS
d/ 2Na + S -to-> Na2S
a) 2Al + 3S -to-> Al2S3
b) Fe + S -to-> FeS
c) Pb + S -to-> PbS
d) 2Na + S -to-> Na2S