A base is a substance that reacts with acids to give salt and water. As proposed by Arrhenius in 1884, the base is a chemical compound that breaks to give hydroxide ions in an aqueous solution. Another definition of base is that base is a substance that accepts protons and gives away elections.
During an acid-base reaction, the hydroxide ion of the base combines with the hydrogen ion of the acid, forming an ionic bond to give salt and water as products, that is, bases have the tendency to accept hydrogen ions.
Bases are classified as Strong base, Neutral base and Weak base depending on their tendency to dissociate into ions. The strong base has the capability to dissociate hydrogen ions or protons even from a weak acid. The weak base is the one that has a lesser tendency to withdraw hydrogen ions or protons from acid during a reaction.
Strong Base vs Weak Base
The main difference between a Strong base and a Weak base is that a strong base ionized completely or 100% in an acid-base reaction or water or solution whereas a weak base is incapable of completely ionizing in a reaction or a solution, it may ionize 1% or 99%. it is still said to be a weak base.
Comparison Table Between Strong Base and Weak Base
| Parameter of Comparison | Strong base | Weak base |
|---|---|---|
| Ionization | Complete ionization. | Incomplete ionization. |
| pH value | 10 to 14. | 7.3 to 10. |
| Reactivity | Strong bases are highly reactive. | Weak bases are less reactive. |
| pKb value | High pKb value. | Low pKb value. |
| Electricity conduction | Strong bases are a good conductor of electricity. | Weak bases are poor conductors of electricity. |
What is Strong Base?
A strong base is a base that holds the capacity to remove proton even from very weak acids or a strong base is that ionizes completely in an aqueous solution or water. They withdraw hydrogen ions from acids during an acid-base reaction.
Strong bases have a 100% dissociation ability. On the pH scale, strong bases measure from 10 to 14.
They have a high equilibrium constant. Strong bases have a high pKb value and a ka value greater than 1. It has a negative pka value. Generally, strong bases are highly soluble in water and other solutions.
The strong bases are highly reactive in nature, therefore, reacts violently with acids in an acid-base reaction. They are also good electrolytes. Strong bases are a good conductor of electricity because the ability to conduct electricity depends on the number of ions present and bases have a concentration of ions.
Some of the examples of strong bases are- Sodium hydroxide (NaOH), Potassium hydroxide (KOH), Lithium hydroxide (LiOH), Calcium hydroxide (Ca(OH)2), Rubidium hydroxide (RbOH), Barium hydroxide (Ba(OH)2), Guanidine, etc. Guanidine is an exceptional case because it remains very stable during protonation.
What is Weak Base?
A weak base is a base that does not have a strong tendency to remove protons from acids. They are the bases that do not ionize completely in water or an aqueous solution. They are not highly capable of withdrawing hydrogen ions from acids in an acid-base reaction. They dissociate partially in a solution.
The weak base may ionize either 1% or 99% but they are still known as a weak base. On the pH scale, weak bases measure from 7.3 to 10. They have a low equilibrium constant as compared to strong bases, the weaker the base the lower is the equilibrium constant. Weak bases are not a good conductor of electricity. They also have a low pKb value also they have a ka value less than 1. They are characterized by positive pka values. They are not highly soluble in water or other solutions.
The weak bases are less reactive in nature and therefore react mildly during an acid-base reaction. They are poor electrolytes and a poor conductor of electricity because they have less concentration of free ions.
Some examples of weak bases are Ammonia (NH3), Pyridine (C5H5N), Alanine, Ethylamine, Dimethylamine, Glycine, Hydrazine, etc. Water itself acts as a weak base.
Main Differences Between Strong Base and Weak Base
- Strong bases ionize completely during a reaction with acid whereas weak bases show an incomplete ionization.
- Strong bases have a higher tendency to accept protons while weak bases have a lower tendency to accept protons.
- When measured on a pH scale, strong bases have a pH between 10 to 14 while weak bases have a pH between 7.3 to 10.
- Strong bases are highly reactive while weak bases are less reactive.
- pKb values of strong bases are high while those of weak bases are low.
- Strong bases are a good conductor of electricity while weak bases are poor conductors of electricity.
- Equilibrium constants of strong bases are high while those of weak bases are low, on the equilibrium scale, as the acid gets weak the value shifts to its left.
- Strong bases are good electrolytes while weak bases are not.
Conclusion
The tendency to dissociate ions defines the strength of a base. Each strong base has a conjugate weak acid and a weak base has its conjugate strong acid.
Strong bases act strongly with acid while weak bases act mildly with acids in an acid-base reaction. Both the bases have their importance and cannot be replaced with one another.
References
- https://journals.co.za/content/saimm/84/9/AJA0038223X_1483
- https://www.osti.gov/biblio/6318391