mathrm(CH)_(2)=mathrm(CH)_(2)+mathrm(HCH)^-

The given chemical equation represents the addition reaction of ethene ( ) with hydrogen chloride ( ). In this reaction, the double bond in ethene breaks, and the hydrogen atom from hydrogen chloride adds to one carbon atom, while the chlorine atom adds to the other carbon atom. This results in the formation of chloroethane ( ). The balanced chemical equation for this reaction is: So, the product of the reaction is chloroethane ( ).