Alkali vs Base
The word alkali is often used interchangeably to address highly basic solutions and alkali metals. In this context, alkali is referred to the alkali metals.
Bases are defined in several ways by various scientists. Arrhenius defines a base as a substance that donates OH- ions to the solution. Bronsted- Lowry defines a base as a substance that can accept a proton. According to Lewis, any electron donor is a base. According to the Arrhenius definition, a compound should have a hydroxide anion and the ability to donate it as a hydroxide ion to be a base. However, according to Lewis and Bronsted- Lowry, there can be molecules, which don’t possess hydroxides, but can act as a base. For example, NH3 is a Lewis base, because it can donate the electron pair on nitrogen. Na2CO3 is a Bronsted- Lowry base without hydroxide groups, but has the ability to accept hydrogens.
Bases have a slippery soap like feeling and a bitter taste. They react easily with acids producing water and salt molecules. Caustic soda, ammonia, and baking soda are some of the common bases we come across very often. Bases can be categorized into two, based on their ability to dissociate and produce hydroxide ions. Strong bases like NaOH, KOH, are completely ionized in a solution, to give ions. Weak bases like NH3 partially dissociate and give fewer amounts of hydroxide ions. Kb is the base dissociation constant. It gives an indication of the ability to lose hydroxide ions of a weak base. Acids with a higher pKa value (more than 13) are weak acids, but their conjugate bases are considered as strong bases. To check whether a substance is a base or not we can use several indicators like litmus paper or pH paper. Bases show a pH value higher than 7, and it turns red litmus to blue.
Alkali is a term commonly used for the metals in the group 1 of the periodic table. These are also known as alkali metals. Although H is also included in this group, it is somewhat different. Therefore, lithium (Li), sodium (Na), potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr) are members of this group. Alkali metals are soft, shiny, silvery color metals. They all have only one electron in their outer shell, and they like to remove this and form +1 cations. When the outer most electrons are excited, it comes back to the ground state while emitting radiation in the visible range. The emission of this electron is easy; thus, alkali metals are very reactive. The reactivity increases down the column. They form ionic compounds with other electronegative atoms. More accurately, alkali is referred to the carbonate or the hydroxide of an alkali metal. They also have basic properties. They are bitter in taste, slippery, and react with acids, to make them neutralized.
What is the difference between base and alkali?
• Group 1 metals are referred as alkali, or more accurately, their carbonates and hydroxides are referred as alkali. However, they have basic properties, thus is a subset of bases.
• So all alkalis are bases, but not all bases are alkalis.
• Alkali is an ionic salt, whereas bases are necessarily not so.