Question

2 H₂O₂(aq) --> 2 H₂O(l) + O₂(g) DH° = −196 kJ/molrxn The decomposition of H₂O₂(aq) is represented by the equation above. A student monitored the decomposition of a 1.0 L sample of H₂O₂(aq) at a constant temperature of 300. K and recorded the concentration of H₂O₂ as a function of time. The results are given in the table below. Which of the following identifies the element(s) being oxidized and reduced in the reaction? a) Hydrogen is oxidized and oxygen is reduced b) oxygen is oxidized and hydrogen is reduced c) oxygen is both oxidized and reduced d) no elements are oxidized or reduced; the rxn is not a redox rxn

Answer 1

In the decomposition of hydrogen peroxide, oxygen is both oxidized and reduced, changing from an oxidation state of -1 in H₂O₂ to -2 in H₂O and to 0 in O₂. Thus, the correct answer is (c) oxygen is both oxidized and reduced.

Step-by-step explanation:

The decomposition of hydrogen peroxide (H₂O₂) is a redox reaction, as it involves changes in the oxidation states of the elements involved. In the reaction 2 H₂O₂(aq) → 2 H₂O(l) + O₂(g), oxygen is being both oxidized and reduced. This is because in H₂O₂, oxygen has an oxidation state of -1. In H₂O, oxygen's oxidation state is -2 (reduction), and in O₂, oxygen's oxidation state is 0 (oxidation). Since the same element, oxygen, undergoes both an increase and a decrease in oxidation state, it is both the oxidized and reduced species in this reaction.

Answer 2

Oxygen in the decomposition of hydrogen peroxide is both oxidized and reduced, making the reaction a disproportionation reaction. Therefore, the answer to which element is being oxidized and reduced is c) oxygen is both oxidized and reduced.

Step-by-step explanation:

The decomposition of H₂O₂ (hydrogen peroxide) into water (H₂O) and oxygen gas (O₂) is represented by the reaction:

2 H₂O₂(aq) → 2 H₂O(l) + O₂(g) ΔH° = −196 kJ/molₓxn

In this equation, oxygen is both oxidized and reduced; making it a disproportionation reaction. Oxygen's oxidation number increases from -1 in H₂O₂ to 0 in O₂, indicating oxidation. Conversely, it decreases from -1 in H₂O₂ to -2 in H₂O, indicating reduction. Therefore, the correct answer is c) oxygen is both oxidized and reduced.