The formulae of four organic compounds are given below:

A - C 2 H 4


C - C 2 H 5 OH

D - C 2 H 6

(i) Which one of these compounds A, B, C or D is a saturated hydrocarbon?

(ii) Identify the organic acid and give its structural formula.


(iii) Which of the above compounds when heated at 443K in the presence of concentrated H 2 SO 4 forms ethene as the major product? What is the role played by concentrated H 2 SO 4 in this reaction? Also, write the chemical equation involved.

(iv) Give a chemical equation when B and C react with each other in presence of concentrated H 2 SO 4 . Name the major product formed and mention one of its important use.




A saturated hydrocarbon is a compound containing only carbon and hydrogen atoms and in which no double or triple bonds are present between any 2 carbon atoms.

Checking all the options

  • C 2 H 4 has a general formula of alkene (C n H 2n ), which means it has a double bond and so is unsaturated .
  • CH 3 COOH and C 2 H 5 OH are not hydrocarbons because along with carbon and hydrogen atoms, oxygen is also present.
  • C 2 H 6 has a general formula of alkane (C n H 2n+2 ), which means it is a saturated hydrocarbon.

Therefore, D is a hydrocarbon.  


Organic acids are compounds which contain a carboxyl functional group(-COOH).

Of these 4 compounds, compound B ie., CH 3 COOH (acetic acid) is the organic acid as it contains the carboxyl functional group. 

Its structure is as follows:

Structure of Ethanol - Teachoo.png

(iii) An alcohol with 2 carbon atoms , when heated at 443K in the presence of conc H 2 SO 4 gives ethene as the main product. 

Compound C i.e. C 2 H 5 OH(ethanol) is an alcohol and has 2 carbon atoms. 

So, when concentrated H 2 SO 4 is added to it, a dehydration reaction takes place where one H 2 O molecule is removed and ethene is formed.

The chemical reaction that takes place is:

Reaction of Ethanol with concentrated H 2 SO 4

Reaction of Ethanol with conc H2SO4 - Teachoo.png


Concentrated H 2 SO 4 here plays the role of dehydrating agent   and removes water from alcohol.

(iv) Compound B is acetic acid and compound C is ethanol.

When an acid reacts with an alcohol , an esterification reaction takes place.

Reaction of acetic acid with ethanol:

Reaction of Ethanol with Acetic acid - Teachoo.png

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Reaction of Ethanol with Acetic acid C2H5OH Ethanol Or Ethyl alcohol CH3COOH Acetic acid Or Ethanoic acidCH3COOC2H5 Ethyl ethanoate Or Ethyl acetate H2O

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CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo