Redox Reactions Quiz

A reducing agent is a substance that causes another substance to undergo reduction, which involves the gain of electrons. In this case, the correct answer states that a reducing agent undergoes oxidation. Oxidation is the process of losing electrons. Therefore, when a reducing agent undergoes oxidation, it donates electrons to another substance, causing that substance to undergo reduction.

The oxidation number of Fe in FeO is +2. In FeO, oxygen always has an oxidation number of -2. Since the overall charge of FeO is neutral, the sum of the oxidation numbers of Fe and O must equal zero. Therefore, the oxidation number of Fe can be calculated as +2 to balance out the -2 oxidation number of O.

The correct answer is Cu2+ (aq) + 2e ---> Cu (s). This is the correct answer because in the half equation, Cu2+ (aq) is being reduced to Cu (s) by gaining 2 electrons. The balanced equation shows the transfer of 2 electrons from the Cu2+ ion to form solid Cu.

The oxidation number of an element refers to the charge that element would have if all the bonds in the compound were ionic. In the case of Na3PO4, sodium (Na) has a charge of +1, and there are three sodium atoms. Oxygen (O) usually has a charge of -2, and there are four oxygen atoms. Therefore, the total charge from sodium and oxygen is +3 and -8 respectively. Since the compound is neutral, the total charge must be zero. This means that the oxidation number of phosphorus (P) must be +5 to balance out the charges and make the compound neutral.

Hydrogen acts as a reducing agent by taking oxygen and giving electrons. In a redox reaction, a reducing agent donates electrons to another species, causing it to be reduced. Hydrogen, being a highly electronegative element, has a strong tendency to attract electrons. Therefore, it can take oxygen from another species and simultaneously donate electrons to it, resulting in the reduction of the other species. This process allows hydrogen to act as a reducing agent.

Electron-accepting species are called oxidizing agents because they have the ability to accept electrons from other species during a chemical reaction. This process is known as oxidation, where the oxidizing agent itself gets reduced by gaining electrons. Therefore, oxidizing agents are substances that facilitate the oxidation of other species by accepting electrons.

The oxidation state of a pure element is zero because in a pure element, all the atoms have an equal number of protons and electrons. Since oxidation state is a measure of the number of electrons gained or lost by an atom in a compound, a pure element does not gain or lose any electrons and therefore has an oxidation state of zero.

When an element is in its highest possible oxidation state in a compound, it means that it has lost or donated all of its electrons. This results in a high positive charge on the element, making it highly electronegative and capable of attracting electrons from other elements. Therefore, it can function as a powerful oxidizing agent, as it has a strong ability to accept electrons and cause other elements to undergo oxidation.

Potassium iodide does not include an oxidizing agent because it is a reducing agent. In chemical reactions, oxidizing agents gain electrons and are reduced, while reducing agents lose electrons and are oxidized. Potassium iodide is commonly used as a reducing agent, as it readily donates its electrons to other substances. Therefore, it cannot act as an oxidizing agent.

The reaction CaCO3 → CaO + CO2 is not a redox reaction because there is no change in the oxidation states of the elements involved. In a redox reaction, there is a transfer of electrons between the reactants, resulting in a change in their oxidation states. In this reaction, calcium carbonate (CaCO3) is simply decomposing into calcium oxide (CaO) and carbon dioxide (CO2), without any change in oxidation states.