What happens when NaOH is added to HCl?

In this article, “naoh + hcl” the product, type of the reaction, and the process to balance this reaction with some relevant topics are discussed briefly.

Table of Contents Show

What happens when NaOH reacts with HCl?
What kind of reaction is NaOH + HCl?
How to balance NaOH + HCl?
Is NaOH + HCl a complete reaction?
Does NaOH + HCl form a precipitate?
NaOH and HCl Titration

NaOH or sodium hydroxide is a strong base and HCl or hydrochloric acid is a strong acid reacts with each other to form sodium chloride (NaCl) and water (H2O). It is basically an acid base reaction which does not form any precipitate after completion of this reaction.

Let’s focus on the following discussions on the reaction between NaOH and HCl.

What happens when NaOH reacts with HCl?

NaOH is a strong base which is dissociated almost 100% in aqueous medium and form sodium cation and hydroxyl anion.

NaOH (aq) = Na+ (aq)+ OH– (aq)

HCl is also a strong acid and dissociates completely in aqueous medium to form hydrogen cation and chloride anion.

HCl (aq) = H+ (aq)+ Cl– (aq)

Now when NaOH is added into the beaker containing hydrochloric acid, due to complete dissociation, Na+ ion from NaOH combines with the Cl– ion of the HCl and form sodium chloride salt. On the other side, H+ ion of HCl and OH– ion from NaOH forms water.

NaOH (aq) + HCl (aq) = NaCl (aq) + H2O (l).

It is an example of double displacement reaction because both the ions from each of the reactant (NaOH and HCl) are displaced with another reactant.

What kind of reaction is NaOH + HCl?

This is an acid-base reaction. Very specifically it is defined as the neutralization reaction in which acid compounds are fully neutralized by the basic compound.

As both the reactants are strong (strong acid and strong base) so no H+ or OH– ions remain unreacted which can affect the Ph of the resultant solution. This is a complete neutralization reaction between a strong acid and strong base. As the solution contains only NaCl and H2O, the pH of the solution will be 7 (neutral pH). This type of reaction is spontaneous towards forward direction due to the formation of stable water (H2O) molecule.

How to balance NaOH + HCl?

To balance any acid-base reaction, the total reaction is divided into its two constituents acid and base part.

Acid part: HCl (aq) = H+ (aq) + Cl– (aq) ——————- 1 no equation
Base part: NaOH (aq) = Na+ (aq) + OH– (aq) ————– 2 no equation

Now both the equation will be multiplied by 1 and the balanced equation is obtained-

HCl (aq) + NaOH (aq) = NaCl (aq) + H2O (l)

There is no need to multiply with any other integer as all the atoms in both the reactant and product sides become same after balancing.

Is NaOH + HCl a complete reaction?

Yes, it will be a complete reaction only if both of the reactant presents in same concentration. Because in neutralization reaction all the Na+ ion formed due to the dissociation of NaOH combines with the Cl– ion, coming from HCl.

No extra H+, OH–, Na+ and Cl– ions are left in reaction medium after completion of reaction. Besides that, no reactants like HCl and NaOH remain as undissociated condition because both are completely dissociated in aqueous medium.

Does NaOH + HCl form a precipitate?

The reaction between HCl and NaOH is a neutralization reaction involving a strong acid and a strong base. It is also known as double displacement reaction due to exchange of both ions of one reactant with another.

The products which are obtained after completion of the reaction is sodium chloride salt and water. NaCl is completely soluble in water. Thus, there is no chance of formation any precipitate after completion of the reaction. The precipitate can only be formed only if the resultant compound is not soluble in the solvent.

NaOH and HCl Titration

For a acid base titration, acid is basically taken in a beaker and base is taken in burette and an indicator is added with acid to detect the end point or equivalence point. These indicators are known as acid-base indicator or pH indicators. In this titration, phenolphthalein is used whose pH lies from the range 8.2 to 10.

NaOH (titrant) is added by drop-wise from burette into the indicator mixed acid solution. When all the H+ ion is neutralized by OH– ion of NaOH, the colour of the resultant solution becomes light pink because base colour of the indicator is light pink and colourless for acid. The point at which exactly enough titrant (NaOH) has been added to react with all the analyte (HCl) is called the equivalence point or end point.

Up to the equivalence point the solution is acidic because of the presence of H+ ion in large excess amount. After the equivalence point the resultant solution will become basic in nature due to excess OH– ion.

Titration curve of NaOH and HCl.
Image Credit: Wikimedia Commons

Conclusion

In the above reaction of NaOH and HCl, the products obtained are sodium chloride salt (NaCl) and water (H2O). This is a neutralization reaction with the pH of the resultant solution will be 7.

Read more about 15 Facts on HCl + CH3COONa.

Answer

Verified

Hint: To solve this we must know that sodium hydroxide $\left( {{\text{NaOH}}} \right)$ is a base and hydrochloric acid $\left( {{\text{HCl}}} \right)$ is an acid. In the reaction, sodium chloride $\left( {{\text{NaCl}}} \right)$ is formed. Sodium chloride is also known as common salt.

Complete step-by-step answer:

i) We are given a reaction in which sodium hydroxide and hydrochloric acid react. The given reaction is as follows:${\text{NaOH}}\left( {{\text{aq}}} \right) + {\text{HCl}}\left( {{\text{aq}}} \right) \to {\text{NaCl}}\left( {{\text{aq}}} \right) + {{\text{H}}_{\text{2}}}{\text{O}}\left( {\text{l}} \right)$We know that sodium hydroxide $\left( {{\text{NaOH}}} \right)$ is a base and hydrochloric acid $\left( {{\text{HCl}}} \right)$ is an acid. In the reaction, sodium chloride $\left( {{\text{NaCl}}} \right)$ is formed. Sodium chloride is a salt. Along with the salt water is also produced in the reaction.The reaction of an acid and a base to produce salt and water is known as neutralization reaction.Thus, the type of given chemical reaction is neutralization reaction.ii) We are given that reaction is exothermic.The chemical reaction in which heat energy is evolved or released or given out by the substance is known as an exothermic reaction. In an exothermic reaction, the net gain in energy is negative.Energy is released in the form of heat or light.iii) Difference between exothermic reaction and endothermic reaction is as follows:

Exothermic reaction	Endothermic reaction
The chemical reaction in which heat energy is evolved or released or given out by the substance is known as an exothermic reaction.	The chemical reaction in which heat energy is absorbed by the substance is known as an endothermic reaction.
Energy is released from the system to the surrounding.	Energy is absorbed from the surrounding by the system.
The released energy is in the form of heat or light.	The absorbed energy is in the form of heat.
Examples: Explosions, nuclear fission, rusting of iron, etc.	Examples: Photosynthesis, melting of ice, evaporation, etc.

iv) Change in temperature as the reaction occurs is as follows:We are given that reaction is exothermic. The chemical reaction in which heat energy is evolved or released or given out by the substance is known as an exothermic reaction. As heat is evolved during the reaction, the temperature of the solution increases. Thus, the temperature of the solution will increase as the chemicals react.

Note: Do not confuse between exothermic reaction and endothermic reaction. The chemical reaction in which heat energy is evolved or released or given out by the substance is known as an exothermic reaction while the chemical reaction in which heat energy is absorbed by the substance is known as an endothermic reaction.