Is Sodium fluoride (NaF) an acid or base or neutral?
Sodium fluoride appears as a white to greenish solid is an inorganic compound with the chemical formula NaF. It is readily soluble in water and generally corrosive to aluminum.
In this article, we will discuss Is Sodium fluoride (NaF) is an acid or base, or salt?
So, Is NaF an acid or base? NaF is a basic salt, due to the formation of OH– radicals when dissolved in an aqueous solution. It is formed from the neutralization of a strong base, namely Sodium hydroxide (NaOH), and a weak acid, namely Hydrofluoric acid (HF).
| Name of Molecule | Sodium fluoride |
| Chemical formula | NaF |
| Molar mass | 41.988 g/mol |
| Nature | Basic salt |
| pH value | >7 |
Why NaF can't be acid in nature?
A compound is said to be acid when it is capable of releasing the proton or H+ ion on dissolving in an aqueous solution. According to Arrhenius’s theory of acid ” A compound is said to be acid when added in water, it increases the number of H+ ions in solution.
Since NaF doesn’t contain any hydrogen ion, it is unable to release the proton in an aqueous solution.
So, as per Arrhenius’s theory, an aqueous solution of NaF doesn’t have any property of acid due to the absence of an H+ ion. Therefore, we can say NaF is not an Arrhenius acid.
Bronsted-Lowry’s theory for an acid state that ” A compound is said to be acid that donates the proton to other species and make conjugate base”.
Therefore, once again NaF doesn’t have any proton, so obvious it is not able to donate the proton to other species.
Hence, NaF is also not a Bronsted-Lowry acid.
Why NaF is a basic salt?
Have you ever heard what these terms mean by “Acidic salt”, “Basic salt”, “Neutral salt”, or “Amphoteric salt”?
Acidic salt: Acidic salt is formed when a neutralization reaction carries out between strong acid and weak base. This type of salt produces an acidic solution after being dissolved in a solvent that has a pH value of less than 7. Examples of acidic salt – NH4Cl, NH4NO3, NH4Br, etc.
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Basic salt: Basic salt is formed when a neutralization reaction carries out between a strong base and weak acid. This type of salt produces a basic solution after being dissolved in a solvent that has a pH value of more than 7. Examples of basic salt – are Na2CO3, Soap, NaCN, etc.
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Neutral salt: This salt has a pH value equal to 7 which means it neither has acidic properties nor basic properties. It is formed when a neutralization reaction carries out between a strong acid and strong base or weak acid and weak base. Examples of neutral salt – are NaCl, KCl, NaNO3, etc.
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Amphoteric salt: This salt can act as acidic salt as well as a basic salt. Or “Amphoteric means the compound has the ability to act as an acid with a base and base with an acid”. Examples of Amphoteric salts – NaHCO3, HCO3–, CH3OH, etc.
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- Why does NaHCO3 act as acid as well as the base?
- Why does HCO3– act as acid as well as the base?
- Why does CH3OH act as acid as well as a base?
Ok, Now come to the point Why does NaF act as basic salt? As we know, Sodium fluoride is formed when NaOH(Strong base) reacts with HF(Weak acid). They react with each other in the molar ratio of 1:1.
⇒ NaOH + HF → NaF + H2O
As per the concepts of salts, a combination of a strong base and weak acid leads to the formation of basic salt.
The nature of salt(acidic or basic) is dependent on the strength of the component in the acid-base reaction.
- An aqueous solution of stronger acid and weak base will acquire more property of acidic rather than a base.
- An aqueous solution of a stronger base and weak acid will acquire more property of basic rather than an acid.
In the case of NaF, a stronger base (NaOH) reacts with a weaker acid(HF), so the aqueous solution of its acquires more property of base rather than an acid.
Hence, we can say NaF is a basic salt in nature.
Why the aqueous solution of NaF becomes basic?
An aqueous solution having a pH value of more than 7 is called a basic aqueous solution.
When sodium fluoride is dissolved in an aqueous solution, it will split into two ions Na+ and F–.
⇒ NaF → Na+ + F–
The Na+ is a cation of strong base(NaOH), hence, it will not undergo hydrolysis in water and doesn’t affect the pH of the solution. But the F– is the anion of a weak acid that gets hydrolysis in water to form HF, leaving OH– ions that make the solution basic.
⇒ F– + H2O → HF + OH–
A weak acid like HF remains undissociated in an aqueous solution or only partially dissociate, hence, the final solution contains more OH– ion than H+ ion.
Therefore, with the presence of additional OH– ions in the aqueous solution, sodium fluoride (NaF) solution becomes basic in nature.
Note: An aqueous solution nature depends on the H+ and OH– ions. When more OH– ions are present in an aqueous solution, then the solution becomes basic, and when more H+ ions are present in an aqueous solution, the solution becomes acidic.
Also, when the number of H+ and OH– ions same in an aqueous solution, then the solution is said to be neutral.
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Is NaF considered strong or weak(acidic or basic salt)?
Sodium fluoride is neither acidic nor basic, it is salt made up of a strong base and weak acid. Strong bases dissociate completely in solution and release a large number of OH– ions but the weak acid mostly remains undissociated and releases fewer H+ ions.
Therefore, with the presence of more OH– ions in an aqueous solution of NaF, we can consider it a strong basic salt.
The concept of acidic salt and basic salt:-
⇒ Strong base + Weak acid = Basic salt (∴ OH– ions > H+ ions)
⇒ Stronger acid + Weak base = Acidic salt (∴ H+ ions > OH– ions)
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Uses of Sodium fluoride
- It is used as an insecticide, pesticide, and rat poison.
- It is used for the manufacture of glasses in various industries.
- It is used in the pharmaceuticals industry to prevent dental cavities.
- It is also used to fluorinate water supplies.
- It is used as a cleansing agent.
Properties of Sodium fluoride
- It has a boiling point of 1,704 °C and a melting point of 993 °C.
- It is generally odorless and appears as a white to greenish solid.
- It is slightly soluble in HF, and ammonia but insoluble in alcohol, acetone, etc.
- It has a cubic crystal structure.
- The molecular shape of NaF is octahedral.
- It is noncombustible and corrosive to aluminum.
Summary
Sodium fluoride is an inorganic compound also known as florocid that has the chemical formula NaF. It is white in color with no odor and highly soluble in water. It is prepared by treating sodium hydroxide with hydrofluoric acid.
- Is sodium fluoride (NaF) acidic or basic salt? Naf is a basic salt. It has a pH value of more than 7. It is made from the neutralization of a strong base (NaOH) with a weak acid (HF).
- The aqueous solution of sodium fluoride (NaF) is basic, due to having more hydroxide ions produced from the hydrolysis of fluoride ions(F– + H2O → HF + OH–).
- The presence of fewer hydrogen ions and more OH– ions, increases the pH level of the NaF solution.
About the author
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
