No, 5.5 is not the neutral pH. When asked about an acid, most would say it’s a corrosive liquid that’d make a hole through any material. Let’s put things right.
Both acids and bases can be dissolved in water and attack living tissue. Acid also attack [react with] many metals and bases don’t. Bases, however, can attack glass. And when an acid and a base meet, neutralization takes place producing salt and water—common salt (NaCl) is just an example of salt.
An example of an acid is hydrochloric acid (HCl) and a base is sodium hydroxide (NaOH), also known as caustic soda. When these two react, they produce sodium chloride [common salt] and water.
Neutralization reaction: HCl + NaOH → NaCl + H2O
Imagine these substances as magnets with a positive and a negative pole (according to the electron charge), which are called ions. The reaction is as simple as swapping halves. In fact, chemical reactions are very much like swinger meetings.
Reaction with ions: H+Cl– + Na+OH– → Na+Cl– + H+OH–
The Swedish chemist Arrhenius was the first to define the concepts acid and base in 1887. An acid was the substance that gave H+ ions and a base released OH– ions, as in the example.
But what’s pH and which is the neutral pH? pH is a measure of acidity. In water it ranges from 0 to 14. As pH decreases to 0, acidity increases. While as pH increases to 14, so does basicity. And right in the middle 7 is the neutral pH; the pH of pure water. So, 5.5 pH of soaps and gels is not the neutral pH, but the pH of our skin, which is slightly acid.
And that’s it. Let it soak in and then we’ll look at later definitions of acid and base.