Question

The pH of a solution of \( 10^{-7} \, \text{M} \, \text{HCl} \) at 25°C is:

• A. 7.0
• B. 6.79
• C. 7.89
• D. 7.69

Hint:

For a \( 10^{-7} \, \text{M} \) strong acid like HCl, the pH will be 7.0 because the concentration of \( H^+ \) ions is \( 10^{-7} \, \text{M} \).

Answer 1

The Correct Option is A

For a \( 10^{-7} \, \text{M} \, \text{HCl} \) solution, the hydrogen ion concentration is equal to the HCl concentration due to complete dissociation of this strong acid in water. At 25°C, the hydrogen ion concentration is \( [H^+] = 10^{-7} \, \text{M} \). The pH is determined by the formula:\[\text{pH} = -\log[H^+]\]Substituting the \( [H^+] \) value:\[\text{pH} = -\log(10^{-7}) = 7.0\]Therefore, the solution's pH is 7.0. Final Answer: \[\boxed{7.0}\]