The element oxidized in the reaction described in PbO2 + 4HCl → 2H2O + PbCl2 + Cl2 is

A. Pb.
B. O.
C. H.
D. Cl.

would the answer be A? please explain

Oxidation is the loss of electrons. Which is losing electrons.

A. Pb is +4 on the left and +2 on the right. That's a gain of electrons so A can't be right.
B. O doesn't change oxidations state. B can't right.
C. H doesn't change oxidation state so C can't be right.
D. Cl changes from -1 on the left to zero on the right which is a loss of electrons. D must be the correct answer.

To determine the element that is oxidized in the given reaction, we need to identify the changes in oxidation states of each element involved.

In the reaction, the reactants are PbO2 (lead dioxide) and HCl (hydrochloric acid), and the products are H2O (water), PbCl2 (lead(II) chloride), and Cl2 (chlorine gas).

The oxidation state of an element indicates the number of electrons it has gained or lost during a chemical reaction. The element that increases its oxidation state in a reaction is considered to be oxidized.

Let's determine the oxidation states of the elements involved:

1. PbO2:
Oxygen (O) usually has an oxidation state of -2. Since PbO2 is a neutral compound, we can assign a +4 oxidation state to lead (Pb).

2. HCl:
Hydrogen (H) usually has an oxidation state of +1. Chlorine (Cl) usually has an oxidation state of -1. Since HCl is a neutral compound, hydrogen has an oxidation state of +1, which means chlorine must have an oxidation state of -1.

3. H2O:
Oxygen usually has an oxidation state of -2. Hydrogen usually has an oxidation state of +1. Since H2O is a neutral compound, the overall oxidation state is 0.

4. PbCl2:
Chlorine (Cl) usually has an oxidation state of -1. Since PbCl2 is a neutral compound, we can assign a +2 oxidation state to lead (Pb).

5. Cl2:
Chlorine exists as a diatomic molecule (Cl2) in its elemental form, so its oxidation state is 0.

Now, let's analyze the elements and their oxidation states before and after the reaction:

- Pb: Its oxidation state changes from +4 (in PbO2) to +2 (in PbCl2). Pb decreases its oxidation state, which means it is reduced, not oxidized.

- O: Oxygen's oxidation state remains -2 throughout the reaction. It is not oxidized or reduced.

- H: Hydrogen's oxidation state changes from +1 (in HCl) to 0 (in H2O). Hydrogen decreases its oxidation state, indicating that it is reduced, not oxidized.

- Cl: Chlorine's oxidation state changes from -1 (in HCl) to 0 (in Cl2). Chlorine increases its oxidation state from -1 to 0, meaning it is oxidized.

Therefore, the element that is oxidized in the reaction is D. Cl (chlorine).