growing up, you constantly hear the term acid and base used to describe liquids such as your water or even a fictional mixture you see on TV. But, what actually is an Acid and a Base? When asking this question it is important to first ask what definition of Acid and Base are you asking for? There are three major definitions of these:
- Arrhenius Definition- an acid generates H+ ions while a base generates OH- ions in solution (acids increase [H+] while bases increase [OH-])
- Brønsted-Lowry Definition– an acid is a proton donor while a base is a proton acceptor
- Lewis Definition– an acid is an electron acceptor while a base is an electron acceptor.
All of these definitions are correct in their own way and you may see different theories used in different situations. The major difference between these definitions is the result of transfer in a solution. Arrhenius acids and bases look purely at the products (H+ and OH-). Brønsted-Lowry looks at the proton exchange while Lewis looks at the electron exchange.
But, how and why are these important? There are many reasons you may be interested in the products of an acid and base or if the acid or base donates or accepts a proton or electron. For example, you may be interested in water reactivity and how it will interact with an acid or base. Another example is the interest in the confirmation and formation of new compounds. Knowing what parts of a compound is an acid or base can tell you what will happen to its structure in specific environments. This can lead to the characteristics of the compound to change and thus change its purpose.
The one tool you always hear in the complement of acids and bases is the pH scale. The pH scale is a way to measure acidity by using the concentration of hydrogen ions in a solution. This scale is typically from 0 to 14 but, the scale can go beyond the normal range. This, however, is extremely rare and means you have a very dangerous material in your possession.
The pH scale is measured using the equation pH=-log([H+]). This means that as you increase the concentration of hydrogen ions in a solution (increase acids), you will see a decrease in the pH scale. Since this scale is measured by log base 10 it is also important to realize that going from a pH of 8 to 4 does not mean you halved the pH and increase the acidity by 2 times. Every increase in a whole number on the pH scale corresponds with a 1×10^10 increase. This means that the change from 8 to 4 would actually be 10,000 times more acidic.
Overall, the general characteristics of Acids and Bases are as follows:
- Good conductors
- pH value less than 7
- Sour in taste
- Bad conductors
- pH value greater than 7
- Bitter in taste