Hydrocarbons: Short Questions and Answers

Question: Give three examples of unsaturated hydrocarbons.

Answer.

Ethene Propene Ethyne

Question: Draw electron dot and cross structures for ethene.

Answer.

Question: Draw the structural formulas of an alkane, an alkene and an alkyne containing five carbon atoms.

Answer.

Pentane

1-Pentene

1-Pentyne

Question: How can you differentiate between ethane and ethene?

Answer.

Bromine water is used to differentiate between ethane and ethane. When bromine water is added to an alkene, the red-brown color disappears. Disappearance of color is due to addition of Br₂ across the double bond.

On the other hand, when bromine water is added to an alkane, red-brown does not disappear.

Question 5: What do you mean by dehydration reaction? Give one example.

Answer.

A reaction in which water is removed from a molecule is called dehydration reaction, e.g.

Question 6: How can you convert :

i. Ethene into ethane

ii, Methane into carbon tetrachloride

iii. Ethene into glycol

iv. Ethyl chloride into ethane

v. Ethyl bromide into ethane

Answer.

ii.

iii.

Ethene Glycol

iv.

Ethyl chloride Ethane

Question 4: Write a chemical equation to show the preparation of an alkane from an alkene and an alkyne.

Answer

Question 5: Write a chemical equation to show the preparation of ethene from dehydration of an alcohol and dehydrohalogenation of alkyl halides.

Answer.

From dehydration of Alcohol

From dehalogenation of alkyl halide

Question 6: Write a chemical equation to show the preparation of ethyne from dehalogenation of 1,2-dihalide and a tetrahalides.

Answer

From 1,2-dihalide : Step 1 and Step 2

From tetrahalide : Step 1 and Step2

Question 7: Write chemical equations showing reaction of KMnO4 with ethene and ethyne.

Answer.

Reaction of KMnO4 with ethene

Reaction of KMnO4 with ethyne

List some industrial uses of ethene and ethyne

Question 8: Explain why a systematic method of naming chemical compounds is necessary.

Answer

Million of organic compounds exist. To understand, recognize and classify these compounds, systematic method of naming these compounds is necessary. An international body '' The international Union of Pure and Applied Chemistry (IUPAC), constantly reviews the rule of naming organic compounds.

Question 9: Draw electron dot and cross structure for

a. Propane b. Propyne c. Propene

Answer

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