p^(3+) p^(2+) Question 8 Which formula/name pair is incorrect? Fe_(3)SO_(3) iron (III) sulfite FeSO_(3) iron(II)sulfite FeS iron(II)sulfide FeSO_(4) iron (II) sulfate Fe_(2)S_(3) iron (III)sulfide Question 9 Which one of the following molecular formulas represents an empirical formula?
The Correct Answer and Explanation is :
Question 8: Incorrect Formula/Name Pair
The formula/name pair that is incorrect is:
FeSO₃ – iron (II) sulfite
Explanation:
FeSO₃ refers to iron (II) sulfite, which is incorrect because the sulfite ion (SO₃²⁻) forms salts with both iron (II) and iron (III), but iron (III), not iron (II), is the most common oxidation state for iron when combined with the sulfite ion.
- Fe₃SO₃ (iron (III) sulfite) is a correct name and formula pair, indicating iron in the +3 oxidation state combined with sulfite.
- FeSO₃ should be iron (III) sulfite, not iron (II) sulfite, as iron (III) typically forms iron (III) sulfite, and iron (II) would form iron (II) sulfite, with a different formula, FeSO₃.
Thus, FeSO₃ should be iron (III) sulfite, not iron (II) sulfite.
Question 9: Empirical Formula
An empirical formula represents the simplest whole-number ratio of the elements in a compound. It does not necessarily reflect the actual number of atoms in a molecule but rather their simplest ratio.
To determine the empirical formula, reduce the number of atoms of each element in the molecular formula to their simplest ratio.
If given molecular formulas for several compounds, the correct empirical formula would be the one that expresses the smallest ratio of the elements in the formula.
For example:
- If a molecular formula is C₆H₁₂, the empirical formula would be CH₂, because both carbon and hydrogen have the same ratio of 1:2.
- A formula like C₆H₁₂O₆ (glucose) is a molecular formula, and its empirical formula would be CH₂O, as it represents the simplest whole-number ratio of the elements.
If you have specific formulas from the options, I can help identify which one is an empirical formula, but in general, it will be the one with the simplest ratio of atoms.