Q8 of 38 Page 100

Write the molecular formula of i. ethane and ii. Ethanoic acid.

(i) The prefix “eth-” corresponds to 2 carbon atoms, and the suffix “-ane” tells us that the compound is an alkane.


Ethane is a saturated hydrocarbon (alkane) containing 2 carbon atoms. The general molecular formula of alkanes is CnH2n+2, where n is the number of carbon atoms. For n=2, we get the molecular formula of ethane which is C2H2x2+2 or C2H6.


(ii) The prefix “eth-” corresponds to 2 carbon atoms, and the suffix “-oic acid” tells us that the compound is a carboxylic acid.


Ethanoic acid is a carboxylic acid containing 2 carbon atoms. One of the carbon atoms is included in the carboxylic acid functional group (-COOH or) and is attached to the carbon atom. The remaining valency is satisfied by hydrogen atoms.


Therefore, the molecular formula is C2H4O2 (CH3COOH).


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Write the molecular formula of the 2nd and 3rd member of the homologous series whose first member is ethane.

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Unsaturated hydrocarbons contain multiple bonds between the two C- atoms and show addition reactions. Give the test to distinguish ethane from ethane.

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What will happen if ethanol reacts with ethanoic acid in the presence of a mineral acid? Name the reaction. Write the chemical equation for this reaction.