Free Gaokao Chemistry: Organic Chemistry Fundamentals Questions and Answers — Questions and Answers
Question 1: Which of the following pairs of substances are isomers of each other?
- Methane (CH4) and Ethane (C2H6)
- Ethanol (C2H5OH) and Dimethyl ether (CH3OCH3) (Correct answer)
- Propene (C3H6) and Propyne (C3H4)
- 1-Propanol and 2-Propanol
Correct answer: Ethanol (C2H5OH) and Dimethyl ether (CH3OCH3)
Isomers are compounds that have the same molecular formula but different structural formulas. Both ethanol (CH3CH2OH) and dimethyl ether (CH3OCH3) share the molecular formula C2H6O, but their functional groups and structures are different, making them isomers.
Question 2: Which of the following organic compounds can decolorize both acidic potassium permanganate (KMnO4) solution and bromine water?
- Ethane
- Ethene (Correct answer)
- Benzene
- Ethanol
Correct answer: Ethene
Ethene contains a carbon-carbon double bond (C=C). This unsaturated bond can undergo an addition reaction with bromine water and an oxidation reaction with acidic KMnO4, causing both reagents to lose their color. Saturated compounds like ethane do not react, while ethanol only reacts with KMnO4.
Question 3: What is the correct IUPAC name for the compound with the structure CH3CH(CH3)CH2COOH?
- 2-Methylbutanoic acid
- 1,2-Dimethylpropanoic acid
- 3-Methylbutanoic acid (Correct answer)
- Isopentanoic acid
Correct answer: 3-Methylbutanoic acid
For naming carboxylic acids, the longest carbon chain including the carboxyl group is identified, and numbering starts from the carboxyl carbon as C1. The chain has four carbons (butanoic acid), and a methyl group is attached to the third carbon (C3).
Question 4: The reaction of benzene with concentrated nitric acid and concentrated sulfuric acid at 50-60°C to produce nitrobenzene is an example of what type of reaction?
- Addition reaction
- Elimination reaction
- Oxidation reaction
- Substitution reaction (Correct answer)
Correct answer: Substitution reaction
This reaction involves the replacement of a hydrogen atom on the benzene ring with a nitro group (-NO2). A reaction where an atom or group of atoms is replaced by another atom or group is known as a substitution reaction. Specifically, this is an electrophilic aromatic substitution.
Question 5: Which of the following statements correctly describes a property of ethanoic acid (acetic acid)?
- It is a strong acid that fully dissociates in water.
- It can react with sodium carbonate to produce CO2 gas. (Correct answer)
- It cannot be oxidized by any common oxidizing agents.
- It is less acidic than ethanol.
Correct answer: It can react with sodium carbonate to produce CO2 gas.
Ethanoic acid is a weak acid, meaning it only partially ionizes in aqueous solution to produce H+ ions and ethanoate ions. Its acidity is greater than that of carbonic acid, allowing it to react with carbonates like sodium carbonate (Na2CO3) to produce carbon dioxide gas.
Question 6: The monomer used to produce the polymer polyethylene is:
- CH2=CH2 (Correct answer)
- CH≡CH
- CH3-CH3
- CH2=CHCl
Correct answer: CH2=CH2
The name 'polyethylene' indicates that the polymer is formed from the polymerization of 'ethylene' monomers. Ethylene is the common name for ethene, which has the chemical formula CH2=CH2. The polymerization process involves the breaking of the pi bond in each ethene molecule to form long saturated chains.
Free Gaokao Chemistry: Organic Chemistry Fundamentals Questions and Answers
Which of the following pairs of substances are isomers of each other?