ACE Your Redox Reactions

Oxidation is defined as the loss of electrons from an atom, ion, or molecule. In this context, the correct answer is "loss of electrons." When an atom or molecule loses electrons, it becomes more positively charged, indicating an oxidation process. Conversely, gain of electrons is known as reduction, which is the opposite of oxidation. The other options, gain of hydrogen and loss of oxygen, are not directly related to oxidation.

A decrease in oxidation state is considered a reduction because it involves the gain of electrons, which is a characteristic of reduction reactions. When an atom or molecule undergoes a decrease in oxidation state, it is gaining electrons and becoming more negatively charged. This gain of electrons is associated with a reduction in the overall oxidation state of the atom or molecule. Therefore, a decrease in oxidation state is a reduction.

The oxidation state of an element is a measure of the number of electrons it has gained or lost in a compound. In the oxide CrO3, there are three oxygen atoms, each with an oxidation state of -2. Since the overall charge of the compound is 0, the oxidation state of chromium (Cr) must be such that the sum of the oxidation states of all the atoms equals 0. By solving the equation 3(-2) + x = 0, we find that x = +6. Therefore, the oxidation state of chromium in CrO3 is +6.

The oxidation state of an element in a compound is a measure of the charge that element would have if all the shared electrons were assigned to the more electronegative atom. In SO32-, the oxidation state of oxygen is -2. Since the overall charge of the ion is -2, the sum of the oxidation states of all the atoms must equal -2. Therefore, the oxidation state of sulfur can be determined by solving the equation: x + 3(-2) = -2, where x is the oxidation state of sulfur. Solving this equation gives x = +4, indicating that the oxidation state of sulfur in SO32- is +4.

In this reaction, magnesium displaces lead ions from the lead(II) sulphate solution. This means that magnesium is undergoing a redox reaction where it is being oxidized, since it is losing electrons in order to displace the lead ions. Therefore, the statement "Magnesium atoms are oxidised" is true.

In the reaction "carbon monoxide + zinc oxide ---> zinc + carbon dioxide", carbon monoxide is acting as a reducing agent. This is because carbon monoxide is oxidized (loses electrons) while zinc oxide is reduced (gains electrons). The carbon monoxide transfers electrons to the zinc oxide, causing the reduction of zinc oxide to zinc and the oxidation of carbon monoxide to carbon dioxide.

In this reaction, hydrogen peroxide (H2O2) is acting as a reducing agent. A reducing agent is a substance that donates electrons to another substance, causing it to be reduced (gain electrons). In the given reaction, the hydrogen peroxide (H2O2) is being oxidized (loses electrons) to form water (H2O) and oxygen gas (O2). The silver oxide (Ag2O) is being reduced (gains electrons) to form silver metal (Ag). Therefore, hydrogen peroxide is behaving as a reducing agent in this reaction.

Acidified potassium manganate (VII) is the compound that takes part in a redox reaction when added to aqueous iron(II) sulphate. This is because potassium manganate (VII) is a strong oxidizing agent and can oxidize iron(II) ions to iron(III) ions. In this reaction, the manganese in potassium manganate (VII) is reduced from +7 oxidation state to +2 oxidation state, while the iron in iron(II) sulphate is oxidized from +2 oxidation state to +3 oxidation state. Therefore, a redox reaction occurs between the two compounds.

Carbon monoxide is a reducing agent because it has a tendency to donate electrons to other substances. In a redox reaction, carbon monoxide can oxidize another substance by giving up electrons, while itself getting reduced. This is due to the presence of a polar covalent bond between carbon and oxygen, where oxygen is more electronegative and attracts the electron density towards itself, creating a partial positive charge on carbon. This makes carbon monoxide a good reducing agent.

The correct answer is "a reducing agent." When acidified potassium dichromate (VI) is used to detect the presence of ethanol vapor, a color change from orange to green occurs. This color change indicates that ethanol is a reducing agent, as it causes the dichromate ion (Cr2O7 2-) in the potassium dichromate solution to be reduced to the green chromium(III) ion (Cr3+). Therefore, ethanol has the ability to donate electrons and cause a reduction reaction to occur.