# 3.11: H+ and OH- Ions- An Introduction to Acids and Bases

Learning Objectives

• To identify H+ as an acid and OH- as a base.

You may have some sense, from your day-to-day experiences, of what chemical substances are considered acids or bases. Most students can identify citric acid as the molecule found in citrus fruits such as lemons and limes. Some students may even know that citric acid and other molecules named as acids are considered to be sour-tasting. You may possibly have heard that sodium bicarbonate (baking soda), which is bitter-tasting, and sodium hydroxide (found in cleaning substances) are considered to be bases. More details about acids, bases, and the reactions they undergo will be discussed in Chapter 10. However, it is worth pointing out the two ions that are used most commonly to identify and distinguish if a substance is acidic or basic, $$\ce{H^{+}}$$ and $$\ce{OH^{−}}$$.

The hydrogen ion, $$\ce{H^{+}}$$, is a cation that is produced when an acid dissolves in water and is therefore one way to identify if a substance is an acid. A base, on the other hand, will produce a hydroxide ion $$\ce{OH^{−}}$$ when dissolved in water.

## Contributor

• Lisa Sharpe Elles, University of Kansas