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For which ONE of the following molecular formulae are CHAIN isomers possible? A C₄H₁₀ B C₃H₈ C C₂H₁₈O D C₃H₈O - NSC Physical Sciences - Question 1 - 2023 - Paper 2
Question 1
For which ONE of the following molecular formulae are CHAIN isomers possible? A C₄H₁₀ B C₃H₈ C C₂H₁₈O D C₃H₈O
Worked Solution & Example Answer:For which ONE of the following molecular formulae are CHAIN isomers possible? A C₄H₁₀ B C₃H₈ C C₂H₁₈O D C₃H₈O - NSC Physical Sciences - Question 1 - 2023 - Paper 2
Step 1
For which ONE of the following molecular formulae are CHAIN isomers possible?
Answer
Chain isomers occur when molecules have the same molecular formula but different structural arrangements of their carbon skeletons. Among the given options:
- A. C₄H₁₀: This molecular formula can have chain isomers, such as butane (linear) and isobutane (branched).
- B. C₃H₈: This does not have chain isomers as it can only exist as propane (no branching possible).
- C. C₂H₆O: This can exist in structural isomers but not in chain isomers since it includes an oxygen atom which limits the variations in carbon chains.
- D. C₃H₈O: Similar to C, while it may have functional isomers, chain isomerism is not applicable because of the presence of oxygen.
Thus, the correct answer is A (C₄H₁₀).
Step 2
Which ONE of the following compounds has the LOWEST vapour pressure under the same conditions?
Answer
To determine which compound has the lowest vapour pressure, consider the intermolecular forces. Compounds with stronger intermolecular forces tend to have lower vapour pressures. In this case:
- A. Alkane (non-polar, weaker forces) may have the highest vapour pressure.
- B. Alkane with more substituents may perform similarly.
- C. Alkane with a long carbon chain generally exhibits lower vapour pressure due to increased van der Waals forces.
- D. The alcohol will likely have the lowest vapour pressure because it has strong hydrogen bonding like the alcohol part.
Thus, the correct answer here is D.
Step 3
The type of organic compound formed when a haloalkane is heated in the presence of a concentrated strong base is …
Answer
The reaction of haloalkanes with a concentrated strong base usually leads to the elimination of hydrogen halide and forms alkenes. The base abstracts a proton from the haloalkane, resulting in the formation of a double bond. Therefore, the correct answer is B (alkene).