Is Bleach a base or an acid?

Bleach is the diluted solution of sodium hypochlorite. It has the chemical formula NaOCl or NaClO and consists of the hypochlorite anion and the sodium cation. It is an anhydrous chemical that may explode upon thermal or mechanical disintegration.

It is commonly used as a disinfectant, bleaching agent, and cleaning agent in homes. It appears yellowish-green in solution. In 1785, Claude Louis Berthollet invented it.

Then, is bleach alkaline? Yes, chlorine bleach is an alkali. Between 11 and 13, sodium hypochlorite has a pH value. It dissociates into hypochlorite anion and sodium ions in aqueous solution. The hypochlorite ions generated in order to accept a proton from water, resulting in the release of OH- ions and a basic solution.

The equation is as follows:

NaClO —-> Na+ + ClO-

Is Bleach an acid?

Acids are chemicals whose aqueous solutions either release protons or receive unshared electron pairs. They have a sour flavour and change blue litmus to red. On the pH scale, all acids have a pH below 7.

Then, is bleach an acid? No, sodium hypochlorite is not acid because its pH is more than 7. In addition, it is neither a proton donor nor an electron acceptor.

In aqueous solution, it changes the colour of red litmus paper to blue, a characteristic of alkalis.

The sodium ion that results from the dissociation of NaClO is neutral, but the ClO- ion possesses an unshared pair of electrons that must be donated.

Bleach is therefore not an acid.

pH of Cleanser

Any solution’s pH indicates its acidity or alkalinity. On the pH scale, values range from 1 to 14.

Any solution with a pH value between 1 and 7 is acidic, while those with a pH value between 7 and 14 are alkaline.

We already know that NaOCl is a basic compound composed of two ions, namely ClO- and Na+.

Therefore, NaOCl’s pH must be less than 7.

Calculating the pH of basic solutions differs from acidic solutions, which simply require a Ka value.

Here, we must first compute the Kb value of the solution, using which the concentration of OH- ions may be determined.

The complete process is as follows:

Prior to estimating the pH of a 0.01 M sodium hypochlorite solution, its Kb value must be determined. The Ka value for this solution is known to be 3 x 10-8.

So, Ka X Kb = 10-14

Consequently, Kb = 10-14/3 x 10-8

= 3.3 X 10-7

Using the value of Kb, calculate the concentration of hydroxide ions.

Kb = ([ClO-] [OH-]) / ([NaClO] – [ClO-])

As, [ClO-] = [OH-]

3.3 X 10-7 = x^2/0.1 − x

[OH-] = 1.8 X 10^-4

Now, the pOH value of the solution is computed utilising the [OH-] value.

pOH = – log [OH]

= 3.7

Moreover, we know that

pOH + pH = 14

pH = 14 – 3.7

= 10.3

Since the pH value is greater than 7, it is evident that NaOCl is basic in nature.

Why is Bleach acidic?

All-Powerful Green Industrial Sodium Hypochlorite Bleach

Several ideas are provided to explain why a material behaves as a base.

Below are three of the most important theories:

According to the Bronsted-Lowry Theory, a material functions as a base if it is able to absorb the protons released by another molecule or particular water in an aqueous solution.

• Arrhenius Hypothesis: According to this theory, a substance is alkaline if it can create hydroxide ions (OH-) in solution.

• Lewis hypothesis: According to this theory, a base is a material with an accessible pair of unshared electrons to donate to other molecules.

Regarding sodium hyper chlorite, the dissociation equation for NaOCl is stated as follows:

NaClO <====> Na+ + ClO-

The Na+ ion that is liberated in this reaction is neutral and has no effect on the nature of the solution.

In the aqueous solution, however, the hypochlorite ion behaves as a proton acceptor. Consequently, according to the Bronsted-Lowry theory, it behaves as an acid.

This reaction results in the creation of hydroxide ions, as shown in the following equation.

ClO- + H2O <====> HClO + OH-

Consequently, the molecule also fits the Arrhenius theory’s criteria for acidic behaviour. Also, because fewer protons reduce the acidity of a solution, the solution becomes more alkaline.

In addition, we know that a negative charge signifies an electron pair that is not shared.

As observed in the preceding reaction, the hypochlorite ion (ClO-) possessed a pair of unshared electrons that it transferred to the hydrogen ion of the water molecule.

Consequently, it likewise functions as a base according to the Lewis theory.

Why is Bleach not an acid?

The definition of acids is derived from the three hypotheses stated above.

These are as follows:

According to the Bronsted-Lowry Theory, a material functions as an acid if it is willing to donate a proton to another molecule.

• Arrhenius Hypothesis: According to this theory, a substance is acidic if it can create hydrogen ions (H+) in a solution.

According to the Lewis theory, an acid is a chemical that takes unshared electron pairs provided by other molecules.

Since none of these requirements are met by sodium hypochlorite, bleach is not an acid.

What is Bleach consist of?

Sodium Hypochlorite – October 2011 Molecule of the Month – HTML-only version

NaOCl, or sodium hypochlorite, is the most common bleach.

One molecule of sodium hypochlorite consists of one sodium atom, one oxygen atom, and one chlorine atom.

As previously indicated, the molecules decompose into sodium and hypochlorite ions.

Regarding its preparation methods, NaOCl is produced by a variety of processes, some of which are listed below:

• Chlorination of soda: In this process, chlorine is carried through sodium hydroxide, resulting in the simultaneous oxidation and reduction of chlorine.

The equation for the reaction is as follows:

Cl2 plus 2 NaOH yields NaCl, NaClO, and H2O.

• Electrolysis of brine: The reaction process is identical to that described in the previous approach, with the exception that the sodium hydroxide and chlorine required for the reaction are created by electrolysis of brine.

• From calcium hypochlorite, sodium carbonate or washing soda is used to treat calcium hypochlorite.

The resulting reaction is as follows:

Na2CO3 + Ca(OCl)2 —–> CaCO3 + 2NaOCl

The sodium chloride reacts with ozone in accordance with the following chemical reaction:

NaCl + O3 —–> NaClO + O2

Properties

Listed below are some features of sodium hypochlorite:

• It seems to be a greenish-yellow solid that exists as a pentahydrate.

• It is represented by the formula NaOCl.

• It is a compound of sodium and hypochlorite ions.

• Its molecular mass is 74.442 grammes per mole.

• The odour is pleasant and chlorine-like.

• Sodium hypochlorite has a density of 1.11 g/cm3

• The melting and boiling points of NaOCl are, respectively, 18°C and 101°C.

At 0 degrees Celsius, its solubility in water is 29.3 grammes per 100 millilitres.

• NaOCl has pKa and pKb values of 7.5185 and 6.4815, respectively.

• Sodium hypochlorite anhydrous is extremely unstable and can easily explode. Nevertheless, the pentahydrate molecule is stable and can be refrigerated.

• It is a very corrosive substance because it is a powerful oxidant.

• It may produce hydrogen with metals, causing the container to explode upon heating.

Uses

Sodium perchlorate is utilised in numerous settings. Some of its applications are listed below:

Bleach is the most common application of sodium hypochlorite. A solution of 3-8 percent NaOCl and 0.01-.002 percent NaOH is utilised. The addition of sodium hydroxide slows down the breakdown processes.

• It is also utilised as a stain remover. It is particularly excellent for removing mould stains, tea or coffee stains on crockery, and dental stains, among others.

• Sodium hypochlorite is also employed as a disinfectant due to its broad-spectrum antimicrobial characteristics. For disinfecting heavily contaminated locations, a 0.5% solution of NaOCl is utilised.

• Dakin’s solution is a solution that contains a little amount of sodium hypochlorite and boric acid.

Due to its oxidation and hydrolysis reactions, it is also utilised to eliminate bad odours. As a result of making organic filth water-soluble and non-volatile, it functions as a deodorizer.

• It is utilised in endodontic procedures due of its efficacy against pathogenic microorganisms. Between 5.5% and 5.25% NaOCl is utilised to disintegrate necrotic tissues and bacterial species.

• Paper and pulp mills use a 10-15 percent sodium hypochlorite solution for water treatment due to its biocidal qualities.

• It is also utilised to eliminate cyanide wastes from water. It converts hazardous cyanide ions to harmless cyanate ions.

• Sodium hypochlorite can also neutralise the nerve agent employed in chemical warfare. The specialists’ Personal Protective Equipment is cleaned with a 50 percent solution of NaOCl.

• A diluted sodium hypochlorite solution is also utilised in the treatment of eczema.

• It is also used to repair skin damage caused by overexposure to the sun, radiation therapy, etc.

• It is also utilised in the detergent and textile industries.

• It is used to sanitise equipment used for food preparation.

• Additionally, it is used to clean swimming pools.

• It is used in the refining of petroleum products.

Conclusion

Bleach, also known as sodium hypochlorite, is a basic with a pH range of 11 to 13.

It dissociates in an aqueous solution into sodium and hypochlorite ions. ClO- ions react further with water molecules, producing hydroxide ions. These hydroxide ions are responsible for sodium hypochlorite solution’s basicity.

In an aqueous solution, sodium hypochlorite molecules receive protons, donate unshared electron pairs, and release OH- ions. Therefore, NaOCl conforms to the Bronsted-Lowry definition of a base.

The acid and base theories of Arrhenius and Lewis, respectively.

Read more: Molecular Form, Lewis Structure, Hybridization, and Polarity of IF5

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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