In the reaction, MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂, which substance is oxidized?
Correct: B
Oxidation is the loss of electrons (increase in oxidation number), and reduction is the gain of electrons (decrease in oxidation number).
Let's analyze the oxidation numbers:
- In MnO₂: Oxygen is -2, so Manganese (Mn) is +4.
- In HCl: Hydrogen is +1, so Chlorine (Cl) is -1.
- In MnCl₂: Chlorine is -1, so Manganese (Mn) is +2.
- In Cl₂ (elemental form): Chlorine (Cl) is 0.
- Manganese changes from +4 (in MnO₂) to +2 (in MnCl₂). This is a decrease in oxidation number, so MnO₂ is reduced.
- Chlorine changes from -1 (in HCl) to 0 (in Cl₂). This is an increase in oxidation number, so HCl is oxidized. Therefore, HCl is the substance that gets oxidized.