To calculate the concentration of ions in a strong acid solution, it is essential to know the identity of the strong acid and its concentration. Strong acids, such as hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and nitric acid (HNO₃), completely dissociate in water.
For example, consider hydrochloric acid (HCl):
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Dissociation: HCl dissociates completely in water as follows:
\[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \] -
Ions produced: For every mole of HCl, one mole of \(\text{H}^+\) ions and one mole of \(\text{Cl}^-\) ions are produced.
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Concentration: If you have a 1 M solution of HCl, then at equilibrium, the concentration of \(\text{H}^+\) ions is 1 M and the concentration of \(\text{Cl}^-\) ions is also 1 M.
Regarding water (\(\text{H}_2\text{O}\)), pure water has a concentration of \(\approx 55.5 , \text{M}\) (since there are about 55.5 moles of water in 1 liter). However, when dealing with acid solutions, this value for water is usually not calculated as it remains nearly constant.
For Sulfuric Acid \( (H_2SO_4) \):
\[ \text{H}_2\text{SO}_4 \rightarrow 2 \text{H}^+ + \text{SO}_4^{2-} \]
For every mole of \( H_2SO_4 \), two moles of \( \text{H}^+ \) ions are produced, along with one mole of \( \text{SO}_4^{2-} \).
Example:
If you have a 1 M solution of \( \text{HCl} \):
- \( [\text{H}^+] = 1, \text{M} \)
- \( [\text{Cl}^-] = 1, \text{M} \)
- \( [\text{H}_2\text{O}] \approx 55.5, \text{M} \) (not included in calculations typically)
If you have a 1 M solution of \( \text{H}_2\text{SO}_4 \):
- \( [\text{H}^+] = 2, \text{M} \)
- \( [\text{SO}_4^{2-}] = 1, \text{M} \)
- \( [\text{H}_2\text{O}] \approx 55.5, \text{M} \) (again typically not included)
To summarize, the calculation of ion concentration depends significantly on the concentration of the strong acid and the specific acid in question.