4 original questions from New Regents. The worksheet, answer key, and browser practice are free.
Checking an Average Charge in an Iron Oxide 4 questions
Checking an Average Charge in an Iron Oxide
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
An iron oxide model uses the formula Fe3O4. Each oxygen in the model has oxidation number −2. The sum of the oxidation numbers in one formula unit is zero. The display allows the iron sites to be +2 or +3.
| Proposed iron sites for one formula unit | Fe at +2 | Fe at +3 |
|---|---|---|
| P | 3 | 0 |
| Q | 2 | 1 |
| R | 1 | 2 |
| S | 0 | 3 |
Question 1
Which proposed set of iron sites balances the four oxygen atoms?
- P
- Q
- R
- S
Question 2
Find the average oxidation number across the three iron sites. Explain how it follows from neutrality.
Write your answer and work on the printable worksheet, or answer online.
Question 3
A student says every iron site must have oxidation number +8/3. Evaluate the claim with the site model.
Write your answer and work on the printable worksheet, or answer online.
A separate liquid model starts with iron ions in the same +2 to +3 ratio. It changes every Fe2+ ion into Fe3+ while spectator ions maintain charge balance.
Question 4
For every three iron ions in the starting ratio, state how many electrons the iron loses during this change.
Write your answer and work on the printable worksheet, or answer online.
2025 Chemistry Reference Tables · Browse Chemistry worksheets