Question

what happen when ethanol react with concentrted H2SO4

Answer 1

 both these reactions, conc.H2SO4acts as a dehydrating agent. The original way to produce diethyl ether was by the dehydration of ethanol byconc H2SO4. Ethanol with a large quantity of excess concentrated sulphuric acid on heating produces ethene. ... Ethanol undergoes dehydration when treated with Conc H2SO4.

Answer 2

ethanol is dehydrated and it forms ethene . sulphuric acid acts only as a catalyst.  the water produced from the reaction gets mixed with sulphuric acid and it gets diluted.

C2H5OH  --- >  C2 H4 + H2 O

in the presence of concentrated  of H2SO4 & high temperature  of 443K