Zinc + Hydrochloric Acid → Zinc Chloride and Hydrogen Gas Zn + 2HCl → ZnCl2 + H2

Explain why it is necessary to place a "2" in front of HCl in the reactants in the chemical equation. Use "evidence" and "scientific" reasoning to support your answer.

This is because you need the same amount of atoms on each side and when you go to the reaction side you see that by adding the coefficient in from the H, 2, the hydrogen and chlorine react to make HCI :))

the answer is b & c i believe : )

every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. therefore, there must be the same number of atoms of each element on each side of a chemical equation.