Question

vegetable oils generally have a long unsaturated carbon chains.give chemical reaction for hydrogenation of vegetable oils

Answer 1

vegetable oils which have long unsaturated hydrocarbons are much healthier than the animal fats which are saturated ones. 

in many industries,they use this process known as hydrogenation.this is where the unsaturated carbons are changed to saturated ones with the help of catalysts( it is a substance that wont affect the chemical reaction but make a path for the reaction to take place ) that help the saturated carbons gain hydrogen and transfer it to saturated ones.
the reaction,


R     R                                         H   H
 I      I      nickel catalyst             I    I
C== C    -------------------------> R-C - C-R
 I      I            adds H2                  I    I
R     R                                         H   H

hope it helps!!!!