Question

Account for the following.
(i) Sunlight is necessary for the substitution reactions of saturated hydrocarbons.
(ii) Ethyne burns with a yellow flame and lots of black smoke.

Answer 1

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(i) Saturated hydrocarbons are most of the time unreactive and are inert in the presence of some reagents. When chlorine is added in saturated hydrocarbons in the presence of sunlight, substitution reaction takes place. Hence,we can say that sunlight is necessary for the substitution reaction of saturated hydrocarbons because it helps in the fastening of reaction.

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(ii) Eth means the presence of two carbons and yne means triple bond which is an unsaturated bond. Now, you know that unsaturated carbon compounds when burnt will always give yellow flame and lots of black smoke, this is the reason why ethyne also gives yellow flame and lots of black smoke when burnt.

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Answer 2

i) Saturated hydrocarbon undergo substitution II) incomplete combustion

Explanation:

• Saturated hydrocarbon undergo substitution reaction where one of its atom is replaced by another usually halogens.
• This happens only in the presence of sunlight as the UV light break down the halogen into free radicles which is necessary for this reaction.
• Ethyne is an unsaturated hydrocarbon with a triple bond. Unsaturated hydrocarbon always produce sooty flames. Hence this burn with yellow flame and lots of black smoke. This is caused due to the incomplete combustion.

To learn more:

1) Chlorine reacts with saturated hydrocarbons at room temperature in the (A) absence of sunlight (B) presence of sunlight:

https://brainly.in/question/5239524

2) Account for the sunlight is necessary for the substitution reaction of saturated hydrocarbons:

https://brainly.in/question/1597532