The rusting of iron is an example of which kind of chemical change?
- A.Reduction
- B.Oxidation
- C.Neutralisation
- D.Decomposition
Correct answer
Explanation
The correct answer is B, oxidation. Rusting is a slow oxidation in which iron combines with oxygen in the presence of moisture to form hydrated iron oxide, the reddish-brown flaky substance we call rust. Both air and water must be present, which is why iron does not rust in dry air or in boiled water free of dissolved oxygen, and why it is protected by painting, oiling, galvanising with zinc or alloying into stainless steel. Option A is wrong because reduction is the removal of oxygen or the gain of electrons, the opposite of what happens to iron here. Option C is wrong because neutralisation is the reaction between an acid and a base to give salt and water, which has nothing to do with rusting. Option D is wrong because decomposition means one compound splitting into simpler substances, whereas rusting builds a new compound. Rusting is one form of corrosion.
Read the full article: Chemical Bonding and Reactions: Types, Rules and Facts
Practice Questions
View allWhich of the following is NOT a double displacement reaction?
- A.BaCl2 + H2SO4 → BaSO4 + 2HCl
- B.2H2 + O2 → 2H2O
- C.CuSO4 + H2S → CuS + H2SO4
- D.NaOH + HCl → NaCl + H2O
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In a double displacement reaction two compounds exchange their ions, so both reactants must be compounds. Here hydrogen and oxygen are elements combining to form a single product, water, which makes it a combination reaction and also a combustion and redox reaction, but certainly not a double displacement.
Read the full explanation →Which among the following compounds has a double bond?
- A.Ethane
- B.Methane
- C.Acetylene
- D.Ethylene
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Ethylene, also called ethene, has the formula C2H4, and its two carbon atoms share two pairs of electrons, which is a carbon-carbon double bond made of one sigma and one pi bond; it is the simplest alkene.
Read the full explanation →The number of sigma and pi bonds in benzene, respectively, is:
- A.12 and 3
- B.3 and 3
- C.6 and 3
- D.9 and 3
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Benzene has the formula C6H6 and a ring of six carbon atoms, each carrying one hydrogen. Count the sigma bonds first: six carbon-carbon bonds around the ring and six carbon-hydrogen bonds give twelve sigma bonds.
Read the full explanation →Which of the following is an amphoteric oxide?
- A.Aluminium oxide
- B.Iron (II) oxide
- C.Magnesium oxide
- D.Carbon dioxide
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An amphoteric oxide reacts with both acids and bases to give a salt and water. Aluminium oxide dissolves in hydrochloric acid to give aluminium chloride and in sodium hydroxide to give sodium aluminate, so it behaves as a base in one case and as an acid in the other.
Read the full explanation →Which of the following is used as a catalyst in the hydrogenation of vegetable oil?
- A.Pb
- B.Ni
- C.H2
- D.He
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Vegetable oils contain unsaturated fatty acids with carbon-carbon double bonds, and when hydrogen is passed through the oil at about 60 degrees Celsius in the presence of finely divided nickel, the double bonds add hydrogen and become saturated, turning the liquid oil into semi-solid vanaspati.
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