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Explain why alkanes and their corresponding alkenes have similar physical properties, but very different chemical properties. - HSC - SSCE Chemistry - Question 17 - 2002 - Paper 1
Question 17
Explain why alkanes and their corresponding alkenes have similar physical properties, but very different chemical properties.
Worked Solution & Example Answer:Explain why alkanes and their corresponding alkenes have similar physical properties, but very different chemical properties. - HSC - SSCE Chemistry - Question 17 - 2002 - Paper 1
Step 1
Explain why alkanes and their corresponding alkenes have similar physical properties
Answer
Alkanes and alkenes both possess similar physical properties due to their similar molecular structures. Both classes of compounds consist of carbon and hydrogen atoms, which leads to similar intermolecular forces, specifically van der Waals forces. These relatively weak forces result in comparable boiling and melting points.
Additionally, the presence of similar molecular weights and sizes in corresponding alkane and alkene pairs means that they exhibit similar solubility in non-polar solvents and similar density characteristics. Overall, the structural similarity is the primary reason for their comparable physical properties.
Step 2
Explain why alkanes and alkenes have very different chemical properties
Answer
The key difference in chemical properties between alkanes and alkenes arises from the types of bonds present in their molecular structures. Alkanes are saturated hydrocarbons, meaning they contain only single C-C bonds, which makes them relatively unreactive and stable.
In contrast, alkenes are unsaturated hydrocarbons containing at least one C=C double bond. This double bond is a region of high electron density, making alkenes more reactive than alkanes. They readily undergo reactions such as addition reactions, where the double bond can be broken to form new compounds. This reactivity difference underlies the contrasting chemical behaviors of these two classes of compounds.