Ethene is obtained by dehydration of ethanol with conc. H₂SO₄ at 433 - 433 K.
\(CH_3- \underset { Ethene }{CH_2 }-OH \xrightarrow [ ]{ Conc.H_2SO_4/433-443K } \underset { Ethene }{CH_2= CH_2 }+H_2O \)

(a) -CO (keto group)
(b) -COOH (carboxyl group)
(c) -CHO (aldehydic group)
(d) -OH (hydroxyl group)

Detergents lower the surface tension of water to a greater extent than soaps and hence detergents are better cleansing agents than soaps.

a) Carboxylic acid having the molecular formula C2H402 must be ethanoic acid (acetic acid)
b) An alcohol which on oxidation with alkaline KMnO 4 followed by acidification gives ethanoic acid must be ethanol.
\(\underset{Ethanol}{CH_3CH_2-OH}\xrightarrow{(i)Alk.KMnO_4/(ii)Dil.H_2SO_4}\underset{Ethanoic\ acid}{CH_3-C=O-OH}\)
c) Since compound X is formed by reaction of ethanoic acid with ethanol in presence of a few drops of conc. H2S04, therefore, compound X must be ester. That is ethyl ethanoate and the reaction is called esterification reaction.
\(\underset{Acetic\ or\ ethanoic\ acid}{CH_3COOH }+ \underset{Ethanol}{C_2H_5OH}\xrightarrow{Conc.H_2SO_4} \underset{Ethyl\ ethanoate}{CH_3COOC_2H_5 }+ \underset{Water}{H_2O}\)
Acetic or ethanoic acid Ethanol Ethyl ethanoate Water

Molecular Formula of Ethyne: C₂H₂ 
Electron dot structure of Ethyne:

Structural formula of Ethyne 
HC≡CH