Question

Complete the reaction.

$$\mathrm{Zn}+2 \mathrm{HCl} \rightarrow$$

Answer 1

When we have to complete any reaction, we have to consider the type of reactions. The different types of reaction in different mediums yields us different products. Recollect on what happens when you react to a metal with an acid.

Complete step-by step answer:
-Upon analysis of the given reaction, we can deduce that this is a redox reaction.
-Redox reaction means that there is a change of the oxidation state. The oxidation state is the degree of the loss of electrons of an atom undergoing a chemical reaction.
-Redox reaction involves oxidation and reduction. Redox reactions are characterized by the actual or formal transfer of electrons between chemical species, most often with one species (the reducing agent) undergoing oxidation (losing electrons) while another species (the oxidizing agent) undergoes reduction (gains electrons).
-The processes of oxidation and reduction occur simultaneously and cannot happen independently of one another. The oxidation alone and the reduction alone are each called a half reaction, because two half-reactions always occur together to form a whole reaction.
-When writing half-reactions, the gained or lost electrons are typically included explicitly in order that the half-reaction be balanced with respect to electric charge. The electrons cancel out when the half-reactions are combined to make the net chemical equation.

Now the given question is:

$$\mathrm{Zn}+2 \mathrm{HCl} \rightarrow$$

The products are $\mathrm{ZnCl}_{2}$ and hydrogen gas.

$$\begin{array}{l} \mathrm{ZnO}-2 \mathrm{e}^{-} \rightarrow \mathrm{Zn}(\mathrm{II}) \text { (oxidation) } \\\ 2 \mathrm{H}(\mathrm{I})+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{H} \text { (reduction) } \end{array}$$

Hence, the net reaction is $\mathrm{Zn}+2 \mathrm{HCl} \rightarrow \mathrm{ZnCl}_{2}+\mathrm{H}_{2}$

Note: Do not confuse redox reaction with acid-base reaction. Acid-base reaction is called neutralisation reaction because they neutralise to form salts. But, redox reactions are not.