To calculate the pH of a hydrochloric acid (HCl) solution, you need to know the concentration of the HCl solution in moles per liter (M).
HCl is a strong acid, meaning it dissociates completely in water:
\[ \text{HCl (aq)} \rightarrow \text{H}^+ (aq) + \text{Cl}^- (aq) \]
The concentration of hydrogen ions \([\text{H}^+]\) in the solution will be equal to the concentration of the HCl solution.
The pH is calculated using the formula:
\[ \text{pH} = -\log[\text{H}^+] \]
Example Calculation
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If you have a 0.1 M HCl solution:
\([\text{H}^+] = 0.1 , \text{M}\)
\[ \text{pH} = -\log(0.1) = 1 \]
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For a 0.01 M HCl solution:
\([\text{H}^+] = 0.01 , \text{M}\)
\[ \text{pH} = -\log(0.01) = 2 \]
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For a 0.001 M HCl solution:
\([\text{H}^+] = 0.001 , \text{M}\)
\[ \text{pH} = -\log(0.001) = 3 \]
Summary
To calculate the pH, simply determine the concentration of the HCl solution, then apply the pH formula. If you provide a specific concentration, I can calculate the exact pH for that concentration.