Gaokao Exam Chemistry: Organic Chemistry Fundamentals 1

Question 1

Which of the following compounds is classified as an ester?

Accepted Answer

CH₃COOCH₂CH₃

Answer

CH₃COOCH₂CH₃ (ethyl ethanoate) contains the ester functional group –COO–, formed by the condensation of a carboxylic acid and an alcohol. CH₃COOH is a carboxylic acid, CH₃OCH₃ is an ether, and CH₃CH₂OH is an alcohol.

Question 2

Propene (CH₃CH=CH₂) reacts with HBr. According to Markovnikov's rule, what is the major product?

Accepted Answer

CH₃CHBrCH₃

Answer

Markovnikov's rule states that in electrophilic addition to an unsymmetrical alkene, H⁺ adds to the carbon bearing the greater number of hydrogen atoms, so Br⁻ adds to the more substituted carbon (C-2), giving 2-bromopropane as the major product.

Question 3

How many structural isomers does the molecular formula C₄H₁₀ represent?

Accepted Answer

2

Answer

C₄H₁₀ has exactly two structural isomers: n-butane (CH₃CH₂CH₂CH₃), a straight chain, and 2-methylpropane (isobutane, (CH₃)₃CH), a branched chain. No other connectivity is possible for four carbons with the saturated formula.

Question 4

Which reagent can be used in the laboratory to distinguish an alkene from an alkane?

Accepted Answer

Bromine water (Br₂/H₂O)

Answer

Alkenes rapidly decolorise bromine water through electrophilic addition across the C=C double bond, turning the orange-brown solution colourless. Alkanes do not react with bromine water under normal conditions and the colour is retained.

Question 5

Which monomer undergoes addition polymerisation to produce the polymer polyethylene (polythene)?

Accepted Answer

Ethylene (CH₂=CH₂)

Answer

Addition polymerisation requires a monomer with a C=C double bond. Ethylene (CH₂=CH₂) contains a double bond that opens repeatedly to link thousands of monomer units into the –(CH₂CH₂)ₙ– chain of polyethylene. The other options lack a polymerisable double bond.

Gaokao Exam Practice Test

Gaokao Exam Practice Test

Gaokao Exam Chemistry: Organic Chemistry Fundamentals 1