How do I complete and balance an equation for reaction of NaOH with HCl?

This reaction involves a base (NaOH) and an acid (HCl), so it's a neutralization reaction, which is a special type of double-displacement reaction. Follow this procedure to write balanced molecular equations for double displacement reactions, when you know only the formulas of the reactants:

Write down the cations and anions present in each of the reactants. You'll have to have memorized a list of common ions to be able to do this! In this case, the NaOH contains Na⁺ and OH^-, and the HCl contains H⁺ and Cl^-.
Swap the ions to build the products. The H⁺ will pair up with the OH^- to produce HOH (water). The Na⁺ and the Cl^- will produce NaCl. Make sure that you combine the cations and anions so that the charges balance.
Label the products as solid, liquid, or aqueous. In general, you'll have to have memorized the solubility guidelines, or looked up the solubilities of the products in a handbook to do this. In this case, though, it's easy: write the water as a liquid, and the NaCl as an aqueous (dissolved) salt.
Does a reaction occur? If one of the products is not a weak electrolyte, a nonelectrolyte, or a solid, no reaction occurs. In this case, water is a weak electrolyte, so a reaction does occur.
Balance the equation. Change the coefficients in front of each compound in the equation so that you have the same number of each type of atom on each side of the equation:
NaOH(aq) + HCl(aq) NaCl(aq) + H₂O(l)
See the section on chemical change for more on this.

Author: Fred Senese senese@antoine.frostburg.edu

General Chemistry Online! How do I complete and balance an equation for reaction of NaOH with HCl?