Question
Complete the following sentence. In a homologous series, as the length of a chain increases the flammability __
Answer
4.1
(268 Votes)
Willow
Expert · Tutor for 3 years
Answer
As the length of a chain in a homologous series increases, the flammability decreases.
Explanation
The homologous series are groups of organic compounds, each series having a specific general formula and functional group. For example, all alkanes which are an example of a homologous series, share the same functional group of -C-C- bonds. As we move along a homologous series (i.e., as the length of chain increases), the physical properties of compounds change gradually. The flammability, in the context of organics, generally stands for combustibility or the ease with which a substance will ignite, causing fire or combustion. For fuels with longer chains (above four carbons), the flames typically get larger as more carbon is available to combust, producing more energy. However, ease of ignition would tend to decrease. This is due to the fact that larger molecules have stronger bonds, which can require additional activation energy for combustion. In essence, for long-chain hydrocarbons alike those found in diesel and paraffin, they are difficult to ignite compared to short-chain hydrocarbons, and they burn with a sooty flame. Meanwhile, short-chain hydrocarbons i.e those found in petrol and butane, have lower ignition temperatures and can ignite very easily and violently, albeit burning with clean flames. Therefore, as the length of chain in a homologous series increases, the ease of ignitability or flammability tends to decrease but it produces more heat energy.