all alkalies are bases but all bases are not alkalies
To understand the relationship between alkalies and bases, we need to first define what these terms mean.
A base is a substance that can accept or donate an electron pair (i.e., accepts a proton). Bases are capable of reacting with acids to form salt and water by a process called neutralization. They typically have a pH greater than 7.
Alkalies, on the other hand, are a subset of bases that are specifically soluble in water. They are usually hydroxides of alkali metals, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). Alkalies are strong bases and have a pH greater than 7.
Now, since bases can be any substance that can accept or donate an electron pair, they include a much wider range of compounds than just alkalies. For example, ammonia (NH3) is a base but not an alkali because it is not soluble in water. Bases can be both weak (partially ionized or dissociated) and strong (completely ionized or dissociated) depending on their ability to react with water.
To determine if a substance is an alkali, you need to check if it is a soluble base, specifically a soluble hydroxide compound of an alkali metal.
In summary, all alkalies are bases because they are a type of soluble base. However, not all bases are alkalies because some bases may not be soluble in water or may not be hydroxides of alkali metals.