Question

A piece of zinc metal is placed in 1.0M solution of hydrochloric acid at ${{25}^{0}}C$. How would you find the net ionic equation of $HCl+Zn\to {{H}_{2}}+ZnC{{l}_{2}}$

Answer 1

Hint: The answer here is based on the concept of balancing the chemical equation that is the number of atoms in the reaction and the product side should be equal and then by seeing through the dissociation process where the ionic equation can be found by combining individual equation.

Complete step by step answer:
The classes of general chemistry tell us about how to balance a chemical equation on the reactant and the product side where the number of moles of reactants should be equal to that of the reactants.
Let us now see what does the ionic equation means and how can that be found.
- The Ionic equation by name itself says that it is in the ionic form which is defined as the equation in which the electrolytes in aqueous solution are expressed as dissociated ions. The net ionic equation is nothing but the equation which lists only those species participating in the reaction.
- Let us first balance the given chemical equation, $HCl+Zn\to {{H}_{2}}+ZnC{{l}_{2}}$
The balanced equation will be:
\[Zn(s)+2HCl(aq)\to ZnC{{l}_{2}}(aq)+{{H}_{2}}(g)\]

We know that hydrochloric acid id the strong acid and therefore it dissociates completely in aqueous solution giving hydrogen ion which is as shown,
\[HCl(aq)\to {{H}^{+}}(aq)+C{{l}^{-}}(aq)\]
Also, zinc chloride is soluble in aqueous solution and also exist as ions that is,
\[ZnC{{l}_{2}}(aq)\to Z{{n}^{2+}}(aq)+2C{{l}^{-}}(aq)\]
Therefore, we can write as,
\[Zn(s)+2\times \left[ {{H}^{+}}(aq)+C{{l}^{-}}(aq) \right]\to Z{{n}^{2+}}(aq)+2C{{l}^{\_}}(aq)+{{H}_{2}}(g)\]
This is nothing but is equivalent to
\[Zn(s)+2{{H}^{+}}(aq)+2C{{l}^{-}}(aq)\to Z{{n}^{2+}}(aq)+2C{{l}^{-}}(aq)+{{H}_{2}}(g)\]
Now, the net ionic equation can be obtained by removing the spectator ions that is by cancelling out the common ion on both reactant and product side, we get
\[Zn(s)+2{{H}^{+}}(aq)\to Z{{n}^{2+}}(aq)+{{H}_{2}}(g)\]
Therefore, the net ionic reaction is nothing but the above given equation.

Note: Note that the spectator ions are nothing but the ion which exists as a reactant as well as product in a chemical equation and this can be observed in the reactions of aqueous solutions usually and this does not affect the equilibrium of the reaction.