how to know if an acid is weak or strong , i simply don't understand the idea of dissolving or not dissolving completely in water ,,,,
The strength of an acid depends upon how completely it dissociates into hydrogen ions and negative ions, not how fully it dissolves.
It relatively easy to remember the common strong acids. HCl, HBr, HI, HClO4, HClO3, H2SO4(the first H ion but not the second), HNO3. There are one or two others but these are the common ones; the other acids are weak.
Determining whether an acid is weak or strong is based on its ability to dissociate or release hydrogen ions (H+) when dissolved in water. Acids that completely dissociate into ions are considered strong acids because they effectively release a larger concentration of H+ ions. On the other hand, weak acids partially dissociate, resulting in a lower concentration of H+ ions.
To determine whether an acid is weak or strong, you can consider the level of dissociation and ionization. Here are three ways to help you identify:
1. Dissociation Equation: Check if the acid dissociates completely or partially. Strong acids, such as hydrochloric acid (HCl), dissociate entirely, producing H+ and Cl- ions. For weak acids, like acetic acid (CH3COOH), they only partially dissociate, resulting in a mixture of undissociated molecules and some H+ and acetate (CH3COO-) ions.
2. Degree of Ionization: It refers to the extent of dissociation of an acid. Strong acids have a high degree of ionization since almost all acid molecules dissociate into ions. In contrast, weak acids have a low degree of ionization, meaning only a small fraction of the acid molecules dissociate into ions.
3. pH Value: The pH value indicates the acidity of a solution. Strong acids completely dissociate, resulting in a higher concentration of H+ ions and a lower pH value. Weak acids, by partially dissociating, provide fewer H+ ions and have a higher pH value (closer to 7), indicating a milder acidity.
Remember that the ability to dissolve completely or partially in water is an indicator of the acid's strength, as it relates to the release of H+ ions. Therefore, the terms "dissolving" and "dissociating" are related in this context.