Question

A compound 'P' on heating with excess conc. H2SO4 forms another carbon compound 'Q' which on addition of hydrogen in the presence of nickel catalyst forms a saturated carbon compound ‘R’. One molecule of ‘R’ on combustion forms two molecules of carbon dioxide and three molecules of water. Identify P, Q and R and write chemical equations for the reactions involved.​

Answer 1

Answer :

$\star\:\rm{P=Ethanol\:(C_2H_5OH)}$

$\star\:\rm{Q=Ethene\:(CH_2=CH_2)}$

$\star\:\rm{R=Ethane\:(C_2H_6)}$

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Reactions involved are:-

1. $\rm{\underset{\text{Ethanol}}{C_2H_5OH}\underset{443\:K}{\xrightarrow{\rm{Conc.\:H_2SO_4}}}\underset{\text{Ethene}}{CH_2=CH_2}+H_2O}$

2. $\rm{C_2H_5OH\underset{H_2}{\xrightarrow{\rm{Nickel\:catalyst}}}\underset{\text{Ethane}}{C_2H_6}}$

3. $\rm{C_2H_6+\dfrac{7}{2}O_2\longrightarrow{}2CO_2+3H_2O}$

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★︎ Extra Information:-

• Reaction 1 represents the reaction of ethanol to give unsaturated hydrocarbon. Heating ethanol at 443 K with excess concentrated sulphuric acid gives ethene as the acid undergoes dehydration.

• Reaction 2 represents an addition reaction. Unsaturated hydrocarbons add hydrogen in the presence of catalysts like nickel or palladium to form saturated hydrocarbon.

• Reaction 3 represents the combustion of the saturated hydrocarbon so formed to give 2 molecules of carbon dioxide and 3 molecules of water.