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Petroleum is a complex mixture of hydrocarbons - VCE - SSCE Chemistry - Question 7 - 2006 - Paper 1
Question 7
Petroleum is a complex mixture of hydrocarbons. The hydrocarbons are mainly alkanes of various carbon chain lengths. a. Write the name and molecular formula of an a... show full transcript
Worked Solution & Example Answer:Petroleum is a complex mixture of hydrocarbons - VCE - SSCE Chemistry - Question 7 - 2006 - Paper 1
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b. Alkanes with short carbon chains boil at lower temperatures than long chain alkanes. Explain, in terms of bonding, why this is so.
Answer
Alkanes with shorter carbon chains have weaker London dispersion forces compared to those with longer chains. The larger the molecule, the greater the surface area and the stronger the dispersion forces, leading to higher boiling points. Therefore, shorter-chain alkanes require less energy to overcome these weaker intermolecular forces, resulting in lower boiling points.
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c. Briefly describe the fractional distillation process that is used for refining petroleum. You may use a fully labelled sketch to answer this question.
Answer
Fractional distillation involves the heating of crude oil in a distillation column, which is divided into various levels. The mixture is vaporized, and as it rises through the column, it cools. Each fraction condenses at different heights according to its boiling point. Lighter fractions, which have lower boiling points, rise higher in the column, while heavier fractions remain lower. These fractions are collected separately for further processing.
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