An organic compound 'X' on heating with cone. H2SO4 forms a compound 'Y' which on addition of one molecule of hydrogen in the presence of nickel forms a compound 'Z'. One molecule of compound 'Z' on combustion forms two molecules of C02 and three molecules of H20. Identify giving reasons the compounds 'X', 'Y' and 'Z'. Write the chemical equations for all the chemical reactions involved.(All India - 2013)
Answers
Answer:X - C2H5OH
Y- C2H4
Z- C2H6
Explanation:C2H5OH = C2H4 + H2O
C2H4 + H2 = C2H6
C2H6 + 4O2 = 2CO2 + 3H2O
The compound 'X' is Ethanol (C₂H₅OH), the compound 'Y' is Ethene (C₂H₄), and the compound 'Z' is Ethane (C₂H₆).
• Let us start collecting hints from backwards. The last clue which is given, says that two molecules of CO₂ and three molecules of H₂O are formed on combustion of Z.
• This implies that 2CO₂ and 3H₂O are formed, and Z is a hydrocarbon, because only hydrocarbons on combustion give CO₂ and H₂O. and 3H₂O are formed, and Z is a hydrocarbon, because only hydrocarbons on combustion give CO₂ and H₂O.
• Now, we know that a hydrocarbon is a compound of carbon and hydrogen. 2CO₂ contains 2 carbon atoms and 3H₂O contains 3 ×2 = 6 hydrogen atoms. Therefore, the molecular formula of Z can be concluded as C₂H₆ (ethane).
C₂H₆ (Z) + (7/2)O₂ + ∆ → 2CO₂ + 3H₂O
• Next, it is given that an addition of one molecule of hydrogen to 'Y' in the presence of nickel forms 'Z' , i.e., ethane.
• We know that an addition of one molecule of hydrogen to an alkene in the presence of nickel catalyst yields an alkane. Therefore, for ethane, the corresponding alkene used should be ethene.
H₂C=CH₂ (Y) + H₂ + Ni → H₃C-CH₃
• Hence, the compound 'Y' is ethene.
• Also, it is given that an organic compound 'X' on heating with conc. H₂SO₄ forms 'Y', i.e, ethene.
• Now, we know that the addition of conc. H₂SO₄ to an alcohol yields the corresponding alkene (dehydration reaction).
• Therefore, the compound 'X' must be an alcohol, and to get ethene, the alcohol used must be ethanol.
C₂H₅OH (X) + conc. H₂SO₄ → H₂C=CH₂ + H₂O