77. MAl2(SO4)3=2Al+3(AS+4AO)=2*27+3(32+64)=342g/mol
342g Al2(SO4)3...............3*32=96g S
39.8g....................................x=11.171g S
78. MCuSO4=ACu+AS+4AO=64+32+64=160g/mol
n=m/M=50/160=0.3126 moli
n=m/MCu==>m=n*MCu=0.3125*64=20g CU
n=m/MS==>m=n*MS=0.3125*32=10g S
n=m/MO==>m=n*MO=0.3125*64=20g O
79. Al=%Al/AAl=20.22/27=0.7488 |||/ (0.7488) --> 1
Cl =%Cl/ACl=79.77/35.5=2.247 ||| (0.7488) --> 3
Formula chimica este AlCl3
