Answer:
CoSO4.7H2O
Cobalt II tetraoxosulphate VI heptahydrate
Step-by-step explanation:
According to IUPAC nomenclature, compounds are named systematically.
We were told that there are seven water molecules in each formula unit Hence the correct formula of the compound is CoSO4.7H2O
According to IUPAC system, the metal is first named, followed by its oxidation state in Roman numerals. Then the name of the anion is mentioned as well as the number of water molecules. We have to take into account the correct prefix signifying the number of molecules of water of crystallization.