Which equation illustrates conservation of mass? O 1 H2 + 1 O2 + 2 H2O
O 1 H2 + 1 2 + 1 H2O
O 1 H2 + 1 Cl2 +1HCI
O 1 H2 + 1 Cl2 + 2HCI

1H₂  +  1Cl₂  →   2HCl

Explanation:

The reaction that illustrates the law of conservation of mass is shown below:  

         1H₂  +  1Cl₂  →   2HCl

According to the law of conservation of mass "in a chemical reaction, matter is neither created nor destroy but atoms are rearranged".

Therefore, we are expected to the end a reaction with the amount of substance we start with.

 Element                                H                                    Cl

Reactants                               2                                      2

Products                                 2                                      2

We see that number of atoms on both sides are the same.