8 original questions from New Regents. The worksheet, answer key, and browser practice are free.
Oxidation Numbers 4 questions
Oxidation Numbers
New Regents original practice • Name: ____________________ Date: __________ Show your work for written answers.
An element alone has oxidation number 0. A monatomic ion’s oxidation number equals its charge. In the compounds here, oxygen has oxidation number −2 and chloride has −1.
Question 1
What is the oxidation number of Fe in elemental Fe(s)?
- −2
- 0
- +2
- +3
Question 2
Calculate the oxidation number of iron in Fe₂O₃. Show how the oxidation numbers sum in this neutral formula.
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Question 3
What is the oxidation number of iron in FeCl₂?
- −2
- −1
- +2
- +3
Question 4
In a model, an Fe³⁺ ion becomes Fe²⁺. State whether the iron is oxidized or reduced and explain using its oxidation number.
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Iron Compound Labels 4 questions
Iron Compound Labels
Use the information below to answer the questions.
A set of sample labels lists these neutral iron compounds. Use the indicated oxidation number for the other element in each compound to compare iron.
| Sample | Formula | Oxidation number of other element |
|---|---|---|
| P | FeO | O is −2 |
| Q | Fe2O3 | O is −2 |
| R | FeCl3 | Cl is −1 |
Question 5
Which samples have iron at the same oxidation number?
- P and Q
- P and R
- Q and R
- P, Q, and R
Question 6
Show the oxidation-number balance for FeCl₃ and state iron’s oxidation number.
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Question 7
If iron changes from the state in P to the state in Q, what happens to its oxidation number?
- It increases from +2 to +3.
- It decreases from +3 to +2.
- It stays at +2.
- It changes from +2 to zero.
Question 8
A student assigns +6 to each Fe in sample Q. Explain how the formula shows the error.
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