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# Acid definition

An acid is a substance that releases hydrogen ions ($\ce{H^+}$) in an aqueous solution. Acids tend to dissociate (break up) into $\ce{H^+}$ ions and negatively charged ions.

An $\ce{H^+}$ ion can be thought of as a proton. Therefore, the dissociation of $\ce{H^+}$ is often called deprotonation.

The general equation for the dissociation of acids is as follows.

$$\ce{HA -> H^+ + A^-}$$

$\ce{A^-}$ represents the anion of the acid. $\ce{A^-}$ would be the chloride ion ($\ce{Cl^-}$) in the case of hydrochloric acid.

The sour taste in foods is caused by acids. Lemons and vinegar both contain acid.

The characteristic sour taste of citrus fruits is due to the presence of citric acid.