Acid and base are the chemical forms that are a significant part of the products that we use daily. They constitute the basic components of a science branch, Chemistry, owing to their widespread use and applications. Both are associated with certain distinct properties that help us distinguish them from each other.
Acid vs Base
“The main difference between acids and bases is that their pH ranges are different. Acids have a pH value of less than seven in an aqueous solution. On the other hand, pH value of more than seven is observed in the case of bases.”
Acids are chemical compounds or substances that release hydronium ions (H+) ions when dissolved in water. They react with bases to form salt and exist in all three physical forms but mostly as solids. They are sour in taste. Acetic acid (CH3COOH) and sulphuric acid (H2SO4) are examples of acids.
Bases are chemical species that release hydroxide ions (OH-) in the aqueous solution. They react with acids forming salt and give a solid appearance, with ammonia being an exception that remains in gaseous form. They are bitter in taste and a bit slippery as well. Examples of bases are Sodium hydroxide (NaOH) and ammonia (NH3).
Comparison Table Between Acid and Base
| Parameters of Comparison | Acid | Base |
| Strength | Depends upon the concentration of hydrogen ions | Depends upon the concentration of hydroxide ions |
| Taste | Sour | Bitter |
| pH range | Less than 7.0 | More than 7.0 |
| Phenolphthalein | Colorless | Pink |
| Methyl orange | Dark red | Yellow |
| Physical characteristics | Solid/liquid/gas | Solid appearance except ammonia (gaseous) |
| Examples | Acetic acid, Sulphuric acid, etc. | Sodium hydroxide, Ammonia, etc. |
What is Acid ?
Acids are the chemical species that elevate the concentration of hydrogen ions when dissolved in water (Arrhenius concept). Different scientists have defined them as per their concept. Lewis termed the ions possessing vacant orbitals and accepting pairs of electrons (acting as electrophiles) as the Lewis acids. In terms of Bronsted Lowry, they are the ones that donate protons.
Most of them are solids, with some being corrosive as well. Acids conduct electricity (electrolytes). They yield hydrogen upon reaction with active metals such as Zn (Zinc), Mg (Magnesium), Al (Aluminium), etc.
Based on the ion dissociation into water, they are divided into two categories. Acids undergoing complete dissociation of ions into water are termed strong acids, for example, HCl (Hydrochloric acid), and HNO3 (Nitric acid). At the same time, those with partial dissociation are referred to as weak acids like HF (Hydrofluoric acid).
What is Base ?
According to the Arrhenius concept, bases are the chemical species that elevate the concentration of hydroxide ions when dissolved in water. An aqueous solution of base is also known to conduct electricity.
Lewis defined bases as the ions possessing lone pair of electrons, thus acting as nucleophiles, and termed them Lewis bases. Bronsted Lowry’s concept defines them as the ones that readily accept the protons.
Bases have also been classified into strong and weak bases based on the extent of dissociation into ions in the water. Strong bases like Sodium hydroxide and Potassium hydroxide completely dissociate into ions. However, weak bases, such as Ammonia and Zinc hydroxide, undergo only partial dissociation of its ions
Main Differences Between Acid and Base
- Acids elevates the concentration of hydrogen ions when dissolved in water whereas bases elevates the concentration of hydroxide ions into the same.
- Acids are considered as proton donators whereas bases are denoted as proton acceptors.
- Acids acts as electrophiles and bases as nucleophiles
- Taste of acids is sour and that of bases is bitter.
- Acids exist in all three forms of matter, that is, solid, liquid and gas but bases mostly give a solid appearance with ammonia being an exception.
- Their pH range is also different. Acids and bases have a pH range of less than seven and more than seven, respectively.
- Acids and bases give different results upon reaction with pH indicators like litmus paper, phenolphthalein and methyl orange. Acids turn litmus paper from blue to red, leaves phenolphthalein colorless and methyl orange, dark red. On the other hand, bases turn litmus paper red to blue, phenolphthalein pink and methyl orange, yellow.
Conclusion
Distinct properties of acids and bases have been thoroughly studied and revised from time to time by researchers and scientists worldwide. It is extremely significant to do so, not just because these chemical forms are the very base of chemistry. But also due to their huge and widespread applications all along the length and breadth of various fields of sciences like pharmaceutical sciences, material sciences, etc.
References
https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/cctc.201700305
https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.200901519?casa_token=5i5c4sdWJdIAAAAA:xVWUDRLIy92Y8IjWoGbzCvQqHD95IQPDjGTHMIEsYLlecFXfdM7UImu2sTEJOgJvZRUVsTRAXz5H7QUhttps://www.sciencedirect.com/science/article/pii/0883944193900012
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