Because many ions and compounds have very similar names,

Solution : Here we have to write the chemical name for the given compounds so that we could distinguish between the names: Step 1: (a) calcium sulfide and calcium hydrogen sulfide: There are 2 compounds : 2+ 1) Calcium sulfide - This compound is made up of Calcium ion(Ca ), it is a metal ion and is a cation and sulfide ion(S ) ion which is a anion. Here charges of both the ions are equal and gets neutralized. Hence, the chemical formula of the given compound is CaS. 2+ 2) Calcium Hydrogen Sulfide - This compound is made up of Calcium ion(Ca ), it is a metal ion and is a cation and hydrogen sulfide ion(HS) ion which is a anion. Here charges of both the ions are not equal hence, charge of one ion becomes subscript of another ion and thus, the chemical formula of the given compound is Ca(HS) . 2 Step 2: (b) hydrobromic acid and bromic acid : The 2 acids are : 1) Hydrobromic acid - The acid name has prefix ‘hydro-’ and suffix ‘-ic’, which indicates that the anion ends with ‘-ide’. The anion here is Bromide ion(Br) and the cation is H since all + acids contain hydrogen atom. Since the charges are equal,it gets neutralized, the chemical formula for the acid is H Br. 2) Bromic acid - The acid name has suffix ‘-ic’, which indicates that the anion ends with ‘-ate’. - + The anion here is Bromate ion(BrO ) and the3ation is H since all acids contain hydrogen atom. Since the charges are equal, it gets neutralized, the chemical formula for the acid is HBrO . 3 Step 3: (c) aluminum nitride and aluminum nitrite : There are 2 compounds : 2+ 1) Aluminum nitride - This compound is made up of Aluminium ion(Al ), it is a metal ion and is a cation and nitride ion(N ) ion which is a anion. Here charges of both the ions gets 3 neutralized as they are equal. Hence, the chemical formula of the given compound is AlN. 2) Aluminum nitrite - This compound is made up of Aluminium ion(Al ), it is a metal ion and 3+ - is a cation and nitrite ion(NO ) ion w2ch is a anion. Here charges of both the ions are not equal hence, charge of one ion becomes subscript of another ion and thus, the chemical formula of the given compound is Al(NO ) . 2 3 Step 4: (d) iron(ll) oxide and iron(lll) oxide : There are 2 compounds : 2+ 1) Iron(ll) oxide - This compound is made up of Iron ion(Fe ), it is a metal ion and is a cation. Here the roman numeral II indicates that the charge of Fe is 2+(Roman numeral is used to indicate its charge as Fe is a transition metal and has multiple oxidation states) and oxide 2- ion(O ) ion which is a anion. Here charges of both the ions gets neutralized as they are equal. Hence, the chemical formula of the given compound is F eO. 2) Iron(lll) oxide - This compound is made up of Iron ion(Fe ), it is a metal ion and is a cation. Here the roman numeral III indicates that the charge of Fe is 3+(Roman numeral is used to indicate its charge as Fe is a transition metal and has multiple oxidation states) and oxide ion(O ) ion which is a anion. Here charges of both the ions are not equal. Hence, the charge of one ion becomes the subscript of another ion and thus, the chemical formula of the given compound is Fe O . 2 3