Find the oxidation number of Al in Al2O3.
The Correct Answer and Explanation is:
To determine the oxidation number of aluminum (Al) in aluminum oxide (Al₂O₃), we need to follow a few steps based on the rules for assigning oxidation numbers:
Step 1: Identify the oxidation state of oxygen.
Oxygen typically has an oxidation number of -2 in most compounds, including aluminum oxide. Since there are three oxygen atoms in Al₂O₃, the total oxidation number for oxygen is:3×(−2)=−63 \times (-2) = -63×(−2)=−6
Step 2: Assign oxidation numbers to aluminum.
Let the oxidation number of aluminum be xxx. Since there are two aluminum atoms in the compound (Al₂O₃), the total oxidation number for aluminum will be:2×x=2×2 \times x = 2×2×x=2x
Step 3: Apply the rule that the sum of oxidation numbers in a neutral compound is zero.
Al₂O₃ is a neutral compound, meaning that the sum of the oxidation numbers of all elements in the compound must be zero. Therefore, we can write the equation:2x+(−6)=02x + (-6) = 02x+(−6)=0
Simplifying this equation:2x−6=02x – 6 = 02x−6=02x=62x = 62x=6x=3x = 3x=3
Conclusion:
The oxidation number of aluminum (Al) in Al₂O₃ is +3.
Explanation:
- Oxygen has a standard oxidation number of -2 in most compounds.
- In a neutral compound like Al₂O₃, the sum of the oxidation numbers of all elements must be zero.
- By applying this rule and knowing the oxidation state of oxygen, we can solve for the oxidation number of aluminum.
- The result shows that aluminum has an oxidation number of +3 in Al₂O₃.
