Hydrogen and hydroxide ions
Acidic and alkaline solutions can conduct electricity because they have ions that are free to carry charge.
Look at the formulae of these acids. They all contain H+ ions.
| Acid name | Formula | Ionic Formula |
| Hydrochloric acid | HCl | H+(aq) Cl-(aq) |
| Sulfuric acid | H2SO4 | 2H+(aq) SO42-(aq) |
| Nitric acid | HNO3 | H+(aq) NO3-(aq) |
| Acid name | Hydrochloric acid |
|---|---|
| Formula | HCl |
| Ionic Formula | H+(aq) Cl-(aq) |
| Acid name | Sulfuric acid |
|---|---|
| Formula | H2SO4 |
| Ionic Formula | 2H+(aq) SO42-(aq) |
| Acid name | Nitric acid |
|---|---|
| Formula | HNO3 |
| Ionic Formula | H+(aq) NO3-(aq) |
When an acid is diluted the concentration of H+ ions is decreased and the pH increases towards 7.
Look at the formulae of these alkalis. They all contain OH- ions.
| Alkali name | Formula | Ionic Formula |
| Sodium hydroxide | NaOH | Na+(aq) OH-(aq) |
| Calcium hydroxide | Ca(OH)2 | Ca2+(aq) 2OH-(aq) |
| Lithium hydroxide | LiOH | Li+(aq) OH-(aq) |
| Alkali name | Sodium hydroxide |
|---|---|
| Formula | NaOH |
| Ionic Formula | Na+(aq) OH-(aq) |
| Alkali name | Calcium hydroxide |
|---|---|
| Formula | Ca(OH)2 |
| Ionic Formula | Ca2+(aq) 2OH-(aq) |
| Alkali name | Lithium hydroxide |
|---|---|
| Formula | LiOH |
| Ionic Formula | Li+(aq) OH-(aq) |
The more concentrated an acid or alkali the better it conducts. When an alkali is diluted the concentration of OH- ions is decreased and the pH decreases towards 7.