2/
Mr(CrCl3)=52+3*35.5=158.5
Mr(MnO2)=55+2*16=87
Mr(H2O)=2*1+16=18
Mr(Li2S)=2*7+32=46
3/
Na(I)2O(II), Ba(II)Cl2(I), N(II)O(II), C(IV)H(I)4
4/
Mr(CrCL3)=158.5
W(Cr)=52/158.5=0.33=33%
W(Cl)=106.5/158.5=0.67=67%
Mr(MnO2)=87
W(Mn)=55/87=0.63=63%
W(O)=32/87=0.37=37%
Mr(H2O)=18
W(H)=2/18=0.11=11%
W(O)=16/18=0.89=89%
Mr(Li2S)=46
W(Li)=14/46=0.3=30%
W(S)=32/46=0.7=70%
6/
m=154 (г)
n=m/M
M(CO2)=12+2*16=44(г/моль)
n=154/44=3.5 (моль)
7/
CuCl2+Zn=ZnCl2+Cu
H2+Br2=2HBr
Вместо знака = пишите стрелочку