Learn Redox Reactions with Free Lessons & Tips

• Oxidation Numbers and Structures:

  • H2SO5: The sum of oxidation numbers in a neutral compound is 0. Since hydrogen has an oxidation state of +1 and oxygen usually has an oxidation state of -2, we can set up the equation: 2x+(−2×5)=02x+(−2×5)=0. Solving for xx, we get x=+5x=+5. Therefore, sulfur has an oxidation state of +5 in H2SO5. The structure of H2SO5 can be suggested as a peroxysulfuric acid, also known as persulfuric acid (H2SO5H2SO5).
  • Cr2O2: The sum of oxidation numbers in a neutral compound is 0. Considering oxygen usually has an oxidation state of -2, we can set up the equation: (2×x)+(2×(−2))=0(2×x)+(2×(−2))=0. Solving for xx, we get x=+2x=+2. Therefore, chromium has an oxidation state of +2 in Cr2O2. However, the compound Cr2O2 does not exist. A possible fallacy in the compound name could be due to misrepresentation or an incorrectly written chemical formula.
  • NOT: The term "NOT" does not correspond to a known chemical compound. Therefore, no oxidation numbers or structures can be assigned.

• Formulas for Compounds:

  • (a) Mercury (II) chloride: HgCl2HgCl2
  • (b) Nickel (II) sulphate: NiSO4NiSO4
  • (c) Tin (IV) oxide: SnO2SnO2
  • (d) Thallium: Thallium can form various compounds, so a specific formula cannot be given without additional information.

• Substances with Variable Oxidation States for Carbon and Nitrogen:

  • Carbon: Carbon can exhibit oxidation states from -4 to +4 in compounds such as methane (CH4CH4), carbon monoxide (COCO), carbon dioxide (CO2CO2), and formaldehyde (H2COH2CO).
  • Nitrogen: Nitrogen can exhibit oxidation states from -3 to +5 in compounds such as ammonia (NH3NH3), nitric acid (HNO3HNO3), nitrogen gas (N2N2), and ammonium chloride (NH4ClNH4Cl).

• Role of Sulphur Dioxide, Hydrogen Peroxide, Ozone, and Nitric Acid as Oxidants:

  • Sulphur dioxide (SO2SO2) and hydrogen peroxide (H2O2H2O2) can act as both oxidizing and reducing agents because they can undergo oxidation and reduction themselves. Ozone (O3O3) and nitric acid (HNO3HNO3) primarily act as oxidants because they have high oxidation potentials and readily donate oxygen atoms or electrons to other substances.

• Instability of AgF2 and Its Strong Oxidizing Property:

  • AgF2 is unstable because silver typically forms compounds with a +1 oxidation state, not +2. If formed, AgF2 would have a highly positive silver ion and highly negative fluoride ions, making it an extremely unstable compound. However, if it were to exist, AgF2 would likely act as a strong oxidizing agent because of the high electronegativity of fluorine and the high positive charge on the silver ion.

• Formation of Compounds of Different Oxidation States in Redox Reactions:

  • In redox reactions, the compound of lower oxidation state is formed when the reducing agent is in excess because the oxidizing agent is fully consumed, leading to the reduction of the other reactant. Conversely, if the oxidizing agent is in excess, the compound of higher oxidation state is formed because the reducing agent is fully consumed, leading to the oxidation of the other reactant.

• Use of Alcoholic Potassium Permanganate in the Manufacture of Benzoic Acid:

  • Alcoholic potassium permanganate (KMnO4KMnO4) is preferred over acidic or alkaline potassium permanganate in the manufacture of benzoic acid from toluene because alcoholic potassium permanganate provides milder conditions for oxidation, leading to better selectivity and higher yields of the desired product. The balanced redox equation for the reaction is as follows: C6H5CH3+2KMnO4+3H2O→C6H5COOH+2MnO2+2KOH+2H2OC6H5CH3+2KMnO4+3H2O→C6H5COOH+2MnO2+2KOH+2H2O

• Fluorine as the Best Oxidant: Fluorine is the most electronegative element, which means it has a strong tendency to attract electrons towards itself. As a result, fluorine readily accepts electrons and undergoes reduction, making it an excellent oxidizing agent. Fluorine has the highest electron affinity and the lowest standard reduction potential among the halogens, making it the strongest oxidant in the group.

3. Chlorine Purification of Water: Excess chlorine in drinking water is harmful to human health. Chlorine reacts with organic matter and forms disinfection by-products (DBPs) such as chloramines and trihalomethanes, which are carcinogenic. To remove excess chlorine, it is treated with sulphur dioxide (SO2SO2):

Cl2+SO2+H2O→HCl+H2SO4Cl2+SO2+H2O→HCl+H2SO4

In this reaction, chlorine (Cl2Cl2) is reduced to hydrochloric acid (HClHCl), while sulphur dioxide (SO2SO2) is oxidized to sulfuric acid (H2SO4H2SO4).