Alternative ways to write a chemical formula and nomenclature: lead(IV) oxide, Pb(NO3)2, iron (II) oxide, hydrogen oxide

Each of the following formulas or chemical names contains an error. Correct each example.

This is the solution in the answer sheet (left side of the equal sign is the question, and the right side is the answer)

2. Pb(NO$$_3$$)$$_3$$ = Pb(NO$$_3$$)$$_2$$

3. iron oxide = iron (II) oxide

4. dihydrogen oxide = hydrogen oxide

To take one of those examples, I know that lead exists both as lead (II) and lead (IV). Would it be wrong to correct the first name to lead (II) oxide rather than lead (IV) oxide?

Can I make similar cases for $$\ce{Pb(NO3)4}$$, iron (III) oxide, and dihydrogen monoxide

Yes, your question is inherently unclear. Except for one, all of your compounds could be wrong in more ways than one. Here’s how:

1. Obviously, lead(III) is not a stable oxidation state of lead; these are lead(II) and lead(IV). However, there are at three different, very common lead oxides (and potentially even more):

• lead(IV) oxide $\ce{PbO2}$ (black)
• lead(II,IV) oxide, also called the lead spinell, $\ce{Pb3O4}$ (orange)
• lead(II) oxide $\ce{PbO}$

Due to their colours, they were commonly referred to as German flag in qualitative inorganic analysis in Munich. Without additional information, it is not possible to determine which lead oxide is meant.

2. Only one lead nitrate is known, to the best of my knowledge; thus $\ce{Pb(NO3)4}$ would be invalid. I do not know why, though, since both nitrate and lead(IV) should be oxidising agents and thus in principle able to combine.

3. The same problem with lead, only worse:

• iron(II) oxide $\ce{FeO}$ (black)
• iron(III) oxide $\ce{Fe2O3}$ (red)
• Wikipedia lists six different iron(II,III) oxides, ranging from $\ce{Fe3O4}$ (the iron spinell) to $\ce{Fe25O32}$.
4. Hydrogen oxide, the answer sheet’s solution, should actually be marked unclear. Dihydrogen oxide clearly refers to water $\ce{H2O}$, but water is not the only hydrogen oxide. The difference here when compared to the previous answers is that it is the oxidation state of oxygen which now varies: $\ce{H2O2}$ might be called dihydrogen dioxide. And in the same vein in which other $\ce{A2B2}$ compounds lose their numerical designators, hydrogen oxide might as well refer to the $1:1$ compound $\ce{H2O2}$. I doubt that was the answer sheet’s intention, though; since dihydrogen oxide is unambiguous.

• I'd suspect lead(IV) nitrate to be prone to decomposition to PbO2 and nitrogen oxides. Dec 11, 2016 at 1:25
• @orthocresol That actually makes a hell lot of sense.
– Jan
Dec 11, 2016 at 1:25
• I would say dihydrogen monoxide is unambiguous; I would debate about dihydrogen oxide. Dec 14, 2016 at 9:21