относительная молекулярная масса: CuCl2, FeS, Al2(SO4)3, MgO, Fe(OH)3​

Mr[CuCl2] = Ar[Cu] + Ar[Cl] * 2 = 63. 546 + 35. 453 * 2 = 134. 452 = 134

Mr[FeS] = Ar[Fe] + Ar[S] = 55. 845 + 32. 065 = 87. 91 = 88

Mr[Al2(SO4)3] = Ar[Al] * 2 + Ar[S] * 3 + Ar[O] * 12 = 26. 9815386 * 2 + 32. 065 * 3 + 15. 9994 * 12 = 342. 1508772 = 342

Mr[MgO] = Ar[Mg] + Ar[O] = 24. 305 + 15. 9994 = 40. 3044 = 40

Mr[Fe(OH)3] = Ar[Fe] + Ar[O] * 3 + Ar[H] * 3 = 55. 845 + 15. 9994 * 3 + 1. 00794 * 3 = 106. 86702 = 107