10 Facts About Acids and Bases

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Acids, Bases, and pH

By Anne Marie Helmenstine, Ph.D.

Here are 10 facts about acids and bases to help you learn about acids, bases, and pH along with a chart for comparison.

1. Any aqueous (water-based) liquid can be classified as an acid, base, or neutral. Oils and other non-aqueous liquids are not acids or bases.
2. There are different definitions of acids and bases, but acids can accept an electron pair or donate a hydrogen ion or a proton in a chemical reaction, while bases can donate an electron pair or accept hydrogen or a proton.
3. Acids and bases are characterized as strong or weak. A strong acid or strong base completely dissociates into its ions in water. If the compound does not completely dissociate, it's a weak acid or base. How corrosive an acid or a base is does not relate to its strength.
4. The pH scale is a measure of the acidity or alkalinity (basicity) or a solution. The scale runs from 0 to 14, with acids having a pH less than 7, 7 being neutral, and bases having a pH higher than 7.
5. Acids and bases react with each other in what is called a neutralization reaction. The reaction produces salt and water and leaves the solution closer to a neutral pH than before.
6. One common test of whether an unknown is an acid or a base is to wet litmus paper with it. Litmus paper is a paper treated with an extract from a certain lichen that changes color according to pH. Acids turn litmus paper red, while bases turn litmus paper blue. A neutral chemical won't change the paper's color.
7. Because they separate into ions in water, both acids and bases conduct electricity.
8. While you can't tell whether a solution is an acid or a base by looking at it, taste and touch may be used to tell them apart. However, since both acids and bases can be corrosive, you shouldn't test chemicals by tasting or touching them! You can get a chemical burn from both acids and bases. Acids tend to taste sour and feel drying or astringent, while bases taste bitter and feel slippery or soapy. Examples of household acids and bases you can test are vinegar (weak acetic acid) and baking soda solution (diluted sodium bicarbonate -- a base).
9. Acids and bases are important in the human body. For example, the stomach secretes hydrochloric acid, HCl, to digest food. The pancreas secretes a fluid rich in the base bicarbonate to neutralize stomach acid before it reaches the small intestine.
10. Acids and bases react with metals. Acids release hydrogen gas when reacted with metals. Sometimes hydrogen gas is released when a base reacts with a metal, such as reacting sodium hydroxide (NaOH) and zinc. Another typical reaction between a base and a metal is a double displacement reaction, which may produce a precipitate metal hydroxide.