Difference Between Acids and Bases

Acids and Bases play an important role in chemistry. We see them everywhere in our day-to-day lives, from our cleaning agents; soaps and detergents, to baking soda. Acids and bases (alkaline earth metal chemical elements) are 2 categories of corrosive substances. Any compound with a pH value between zero to seven is considered acidic, whereas a pH value between seven to fourteen is a base. An acid is called a proton donor, while a base is called a proton acceptor (Kolb, 1978).

Difference in Definition

Acid

An acid is a molecule or substance that has a pH value of less than 7.0 when it is present in an aqueous solution. An aqueous solution is any solution where water is a solvent. Acids are termed as compounds that donate H⁺ (hydrogen ion) to another compound known as base.

Base

A base (alkaline) is a molecule or substance that has a pH value higher than 7.0 when present in an aqueous solution. Bases are the exact chemical opposite of acids. In chemistry. They are substances that, in an aqueous solution, release hydroxide (OH⁻) ions.

Arrhenius Concept (Ouertatani et al, 2007)

Acids

As per Arrhenius Concept, an acid elevates the concentration of Hydrogen ions when dissolved in water.

Bases

As per Arrhenius Concept, a base is a compound that increases the concentration of hydroxide ions (OH^–) when dissolved in water.

Bronsted-Lowry Concept (Kauffman, 1988)

Acids

In the Bronsted-Lowry Concept, acids are substances that donate protons

Bases

Bases, on the other hand, are substances that accept protons

Lewis Concept (Brewer, 1984)

Acids

Ions that accept the pair of electrons (electron pair acceptor – an electrophile), and possess vacant orbitals are termed ‘Lewis acid’.

Bases

Ions that donate a pair of electrons (electron-pair donor – a nucleophile), and possess a lone pair of electrons are termed ‘Lewis base’.

Difference in Classification

Acids

Acids are classified as:

• Strong acids, such as nitric acid (HNO₃), sulfuric acid (H₂SO₄), and hydrochloric acid (HCl) respectively.
• Strong Lewis acids, such as AlCl₃ (anhydrous aluminum chloride) and BF₃ (boron trifluoride).
• Concentrated weak acids, such as acetic acid (CH₃COOH) and formic acid (CH₂O₂).
• Lewis acids with specific reactivity, for example; solutions of Z_nCl₂ (zinc chloride).
• Superacids, are extremely strong acids.

Bases

Bases are classified as:

• Alkalis or Caustics, such as NaOH (sodium hydroxide) and KOH (potassium hydroxide).
• Concentrated weak bases, such as NH₃ (ammonia) in a concentrated solution.
• Alkali metals in metallic form, (i.e. elemental sodium), and hydrides of alkaline and alkali earth metals, i.e. NaH (sodium hydride), which function as a strong hydrate and bases to produce caustics.
• Superbases, which are extremely strong bases, such as metal amides, alkoxides, (i.e. NaNH₂ – sodium amide), and C4H9Li (butyllithium), which is an organometallic base.

Difference in Chemical Formula

Acids

The chemical formula for most acids starts with H. For Examples, Nitric acid (HNO₃), Carbonic acid in soft drinks (H₂CO₃), Boric acid (H₃BO₃), Hydrochloric acid (HCl), Oxalic Acid (H₂C₂O₄), Citric Acid or 2-Hydroxy-1,2,3-propane tricarboxylic acid (H₃C₆H5O₇), and Sulfuric acid (H₂SO₄). However, there are exceptions like Acetic Acid (CH₃COOH).

Bases

The chemical formula for most bases (compounds) has OH at the end. For example, Calcium hydroxide or slaked lime, Ca (OH)₂ (paper, flocculant), Magnesium hydroxide (Mg (OH)₂) or milk of magnesia, Sodium hydroxide (NaOH) or caustic soda (cleaning agent, pH regulator), Ammonium hydroxide (NH₄OH) or ammonia water and KOH (Potassium hydroxide).

Difference in pH

Acids

Acids have a pH of less than 7.0.

Bases

Bases have a pH higher than 7.0, and could even go up to 14 if the bases are very strong.

Strength of Acids and Bases

Acids

The strength of acids depends on the concentration of hydronium ions (Umansky, 1991).

Bases

The strength of bases depends on the concentration of hydroxide ions.

Differences in Physical Characteristics

Both acids and bases are different in their physical properties.

Acids

When dissolved in water, acids

• Are Sticky
• Have a burning sensation
• Change blue litmus to red color
• Are sour in taste
• React with bases for neutralization of their properties
• Conduct electricity
• React with active metals to liberate H (Hydrogen)
• Remain colorless when Phenolphthalein is added to the solution.

Bases

When dissolved in water, bases

• Are bitter in taste
• Are (except ammonia)
• Change red litmus to blue color
• Are slippery to the touch
• React with acids to neutralize their respective properties
• Turn pink when Phenolphthalein is added to the solution.

Difference in Ionization

Acids

Acids are species or compounds that break apart in H₂O to form a hydrogen ion (H⁺). So, it can be said that acids form Hydronium ions on ionization (Schultz, 1997).

Bases

Bases result in Hydroxyl ions on ionization (Nyasulu et al, 2013).

Difference in Dissociation

Acids

Acids release H⁺ (Hydrogen ions) when mixed with water (H₂0).

Bases

Bases release OH^– (Hydroxide ions) when mixed with water (H₂0).

Differences in Uses

Acids

• Used for household cleaning.
• Used for industrial purposes: Acids, i.e. Sulfuric acid and Nitric acid are both commonly used in paints, dyes, fertilizers, and explosives.
• Used as a metal dissolver: Hydrochloric acid (HCl) is used to make aqua regia, which assists in dissolving noble metals like platinum and gold (Jadhav & Hocheng, 2015).
• Acids (i.e. Sulfuric acid) are used to make batteries for flashlights and cars. Sulfuric acid is also used in mineral processing (Ntengwe, 2010).
• They are used to ward off rust and corrosion from metals, by means of a technique termed ‘pickling.’
• In the chemical industry, acids are used as neutralizers in the production of salts. For example, nitric acid (HNO₃) reacts with ammonia NH₃ for the production of ammonium nitrate – a fertilizer.

Bases

• Sodium hydroxide (NaOH) is used in manufacturing soap, synthetic fiber rayon, and paper. It is also used in manufacturing some medicines and petroleum-refining, in cleaning sinks, ovens, and drains (Malkin, 2003).
• Sodium bicarbonate (NAHCO₃) is used in toothpaste, fire extinguisher, and baking soda.
• Calcium hydroxide (slaked lime) is used in the manufacture of bleaching powder. It is mixed with water and sand to create mortar that is used in the construction of buildings. Slaked lime is also made used by the farmers on the fields for neutralizing the dangerous effects of acid rain. Calcium hydroxide also neutralizes the acid in water supplies and is used as a dressing material for burns caused by acid, as an antidote for cases of food poisoning, in the making of fungicides, in the whitewash mixture, and in dentistry (Smith et al, 2014) (Mohammadi & Dummer, 2011).
• Alkalis (Bases) are used in alkaline batteries like potassium hydroxide (Salkind, & Klein, 2000). They are also used in antiperspirant armpit deodorant, and in neutralizing soil acidity (Stenzaly‐Achtert et al, 2000) (Merry, 2009).
• Ammonium hydroxide (NH₄OH) is used to clean grease stains from clothes (Malanova et al, 2014).

Comparison Chart – Acids VS Bases

Conclusion

Acids and bases impact daily life because they play a major and important role in many reactions, from digesting food to removing soap scum off a shower wall. Acids and bases are significant in balancing the pH levels in the body so that it stays at a level of 7. When a person consumes acidic foods, the body uses a buffering system to neutralize the positive ions produced by the acids. On the other hand, bases are required to regulate and control the body from becoming too alkaline.

We conclude that both acids and bases are an important part of life, and are found in the environment, in foods, and in chemicals, including pharmaceuticals. They are vital, not only in the chemistry laboratory but also in our daily lives.

References

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