What is the equation for the reaction of 1,2-dichloroethene with hydrogen chloride?

The first step to balancing this equation is to convert the words into chemical formulas. From your question, we are able to write:

1,2-dichloroethene with hydrogen chloride = C2H2Cl2 + HCl

Next, we need to determine the type of reaction and the products formed.

C2H2Cl2 + HCl → C2H4 + Cl2

During a chemical reaction, the bonds of the reactants are broken. The atoms of the reactants are then rearranged to form new products. According to the law of conservation of matter, matter cannot be created nor destroyed. Therefore, we need to check that chemical equation is balanced by making sure there are equal numbers of each type of atom on either side of the equation.

C2H2Cl2 + HCl → C2H4 + Cl2

C =2                       C = 2

H = 3                     H = 4

Cl = 4                    Cl = 2

The hydrogens and chlorines are not equal on both sides. Thus, the equation needs to balanced using coefficients. The final, balanced equation is written below.

C2H2Cl2 + 2HCl → C2H4 + 2Cl2