[tex]Ca (OH)_2 + 2HCl \rightarrow Ca Cl_2 + 2H_2 O[/tex]
Explanation:
First of all, let's try to identify the different substances involved in the reaction:
- calcium hydroxide: calcium is the element [tex]Ca[/tex], while hydroxide corresponds to the ion [tex]OH^-[/tex]. Calcium has 2 valence electrons, so the calcium ion is [tex]Ca^{2+}[/tex], and since the ion [tex]OH^-[/tex] has only one negative charge, we need two of them to combine with the calcium ion, therefore: [tex]Ca(OH)_2[/tex]
- hydrochloric acid: this is an acid, so with one ion of hydrogen [tex]H^+[/tex], and the other element is the chlorine, which in the ion form is [tex]Cl^-[/tex], so the hydrochloric acid is [tex]HCl[/tex]
- calcium chloride: this is the combination of the calcium ion, [tex]Ca^{2+}[/tex], with the chlorine ion, [tex]Cl^-[/tex], so the compound is [tex]CaCl_2[/tex]
- Water: this is given by [tex]H_2 O[/tex]
so, the reaction is
[tex]Ca (OH)_2 + HCl \rightarrow Ca Cl_2 + H_2 O[/tex]
However, this reaction is not balanced yet: in fact, we have 2 atoms of oxygen on the left and only one on the right. Moreover, we have 3 atoms of hydrogen on the left and only 2 on the right. Therefore, in order to balance it, we must write:
[tex]Ca (OH)_2 + 2HCl \rightarrow Ca Cl_2 + 2H_2 O[/tex]
