- An oxidising agent is the species that oxidise a substance by taking electrons from it whereas reducing agent is the species that reduces a substance by donating electron to it. Almost all metals are good reducing agents because they have the tendency to lose electrons whereas non-metals are mostly oxidizing agents because they accept electrons from a substance.
States the difference between oxidising and reducing agents.
Define electrophile and nucleophile
Electrophile is an ion or
molecule that is electron deficient and can accept electrons. Electrophiles are
often reducing agents and Lewis acids. They are either positive ions (e.g. NO2+)
or molecules that have a positive charge on a particular atom (e.g. SO3,
which has an electron deficient sulphur atom). In organic reactions they tend
to attack negatively charged parts of a molecule. Types of electrophiles: Lewis
acids, cations and electron deficient sites in organic compounds
Nucleophile is an ion or
molecule that can donate electrons. Nucleophiles are often oxidizing agents and
Lewis bases. They are either negative ions (e.g. Cl–) or molecules
that have electron pairs (e.g. NH3). In organic reactions they tend
to attack positively charged parts of a molecule. Types of nucleophiles: Lewis
bases, anions and electron rich sites in organic compounds.
SPM Form 5: Oxidation and Reduction (Checklist)
- Oxidation: A reaction that occurs when a substance gains oxygen.
- Oxidizing agent: The substance that oxidizes other reacting substances in a reaction while it is being reduced.
- Reduction: The reaction that occurs when a substances loses oxygen.
- Reducing agent: The substance that reduces other reacting substances in a reaction in a reaction while it is being oxidized.
- Redox reaction: A chemical reaction in which oxidation and reduction occur simultaneously.
- Metal displacement reaction: A reaction where a more electropositive metal replaces a less electropositive metal from its salt solution. In a metal displacement reaction, a more electropositive metal acts as the reducing agent whereas the ion of the less electropositive metal in the salt solution acts as the oxidizing agent.
- Halogen displacement reaction: A reaction where a more reaction halogen replaces a less reactive halogen from its halide solution. In a halogen displacement reaction, a more reactive halogen acts as the oxidizing agent whereas the halide ion of the less reactive halogen acts as the reducing agent.
- Rusting of iron = the corrosion of ion. Rusting can be prevented when iron is in contact with a more electropositive metal. Rusting occurs faster when iron is in contact with a less electropositive metal.
- Reactivity series of metals: A list of metal that are arranged according to their reactivity with oxygen. The descending order of reactivity of metal with oxygen is magnesium, zinc, iron, lead and copper.
- Carbon is placed between aluminium and zinc in the reactivity series. Magnesium is placed higher than carbon in the reactivity series. Carbon acted as a reducing agent because the metal oxide was reduced to metal in the presence of carbon.
- Hydrogen is placed between zinc and iron in the reactivity series. Hydrogen gas acted as a reducing agent because the metal oxide was reduced to metal in the presence of hydrogen gas.
- In an electrolytic cell, oxidation takes place at the anode whereas reduction takes place at the cathode.
- In a chemical cell, oxidation takes place at the negative terminal (anode) whereas reduction takes place at the positive terminal (cathode).