Относительная молекулярная масса каждого соединения вычисляется путем сложения атомных масс каждого атома в молекуле.

AL2O3: 2$Al$ + 3$O$ = 2$26.98$ +3$16.00$ = 101.96 g/mol
CrSO4: Cr + 1$S$ + 4$O$ = 52.00 + 32.06 + 4$16.00$ = 159.06 g/mol
BaCO3: Ba + C + 3$O$ = 137.33 + 12.01 + 3$16.00$ = 197.34 g/mol
AlPO4: Al + P + 4$O$ = 26.98 + 30.97 + 4$16.00$ = 121.97 g/mol
Cu$OH$2: Cu + 2$O$ + 2$H$ = 63.55 + 2$16.00$ + 2$1.01$ = 97.56 g/mol
Mg3B2: 3$Mg$ + 2$B$ = 3$24.31$ + 2$10.81$ = 94.00 g/mol
Fe3O4: 3$Fe$ + 4$O$ = 3$55.85$ + 4$16.00$ = 231.52 g/mol
CaCO3: Ca + C + 3$O$ = 40.08 + 12.01 + 3$16.00$ = 100.09 g/mol
BaSO4: Ba + S + 4$O$ = 137.33 + 32.06 + 4$16.00$ = 233.33 g/mol
Cr$OH$3: Cr + 3$O$ + 3$H$ = 52.00 + 3$16.00$ + 3$1.01$ = 101.03 g/mol
Al$NO3$3: Al + 3$N$ + 9$O$ = 26.98 + 3$14.01$ + 9$16.00$ = 213.00 g/mol
Mg3$PO4$2: 3$Mg$ + 2$P$ + 8$O$ = 3$24.31$ + 2$30.97$ + 8$16.00$ = 262.88 g/mol
Cr2$SO4$3: 2$Cr$ + 3$S$ + 12$O$ = 2$52.00$ + 3$32.06$ + 12$16.00$ = 392.18 g/mol
$NH4$2SO4: 2$NH4$ + S + 4$O$ = 2$18.04$ + 32.06 + 4$16.00$ = 132.14 g/mol
Cr$OH3$2: Cr + 3$O$ + 2$H$ = 52.00 + 3$16.00$ + 2$1.01$ = 95.03 g/mol
$NH4$2HPO4: 2$NH4$ + H + P + 4$O$ = 2$18.04$ + 1.01 + 30.97 + 4$16.00$ = 132.06 g/mol
Hg$NO3$2: Hg + 2$N$ + 6$O$ = 200.59 + 2$14.01$ + 6$16.00$ = 324.56 g/mol
Cr$SiO3$3: Cr + 3$Si$ + 9$O$ = 52.00 + 3$28.09$ + 9$16.00$ = 308.27 g/mol

Таким образом, относительная молекулярная масса каждого соединения составляет:
AL2O3 - 101.96 g/mol
CrSO4 - 159.06 g/mol
BaCO3 - 197.34 g/mol
AlPO4 - 121.97 g/mol
Cu$OH$2 - 97.56 g/mol
Mg3B2 - 94.00 g/mol
Fe3O4 - 231.52 g/mol
CaCO3 - 100.09 g/mol
BaSO4 - 233.33 g/mol
Cr$OH$3 - 101.03 g/mol
Al$NO3$3 - 213.00 g/mol
Mg3$PO4$2 - 262.88 g/mol
Cr2$SO4$3 - 392.18 g/mol
$NH4$2SO4 - 132.14 g/mol
Cr$OH3$2 - 95.03 g/mol
$NH4$2HPO4 - 132.06 g/mol
Hg$NO3$2 - 324.56 g/mol
Cr$SiO3$3 - 308.27 g/mol