Final answer:
The equation that best represents the reaction between Zn metal and NiCl2 is Zn + NiCl2 → ZnCl2 + Ni, which is a single replacement reaction.
Step-by-step explanation:
The correct equation that represents the reaction between Zn metal and NiCl2 is Zn + NiCl2 → ZnCl2 + Ni. This is a single replacement reaction where zinc metal replaces nickel in nickel(II) chloride to form zinc chloride and nickel metal. In this type of reaction, the metallic element (zinc in this case) displaces another metal (nickel) from its compound.
Each substance in the chemical equation must have its correct formula based on the charges of the ions. Zinc forms ions with a +2 charge, and so does nickel in nickel chloride. Therefore, for every one mole of zinc, one mole of nickel chloride is required to react and produce one mole of zinc chloride and one mole of nickel metal. This is according to the principle of conservation of mass, which requires that the number of atoms for each element be the same on both sides of the reaction.