Questions: If a sample of a certain solution is determined to have a [H3O+] concentration of 6.69 × 10^-13 moles/liter, what is its pH? Round off your answer to one decimal place.

Solution Steps

The pH of a solution is calculated using the formula: \[ \text{pH} = -\log_{10} \left[\mathrm{H}_3\mathrm{O}^+\right] \] where \([\mathrm{H}_3\mathrm{O}^+]\) is the concentration of hydronium ions in moles per liter.

Given the concentration of hydronium ions is \(6.69 \times 10^{-13}\) moles/liter, we substitute this value into the pH formula: \[ \text{pH} = -\log_{10} (6.69 \times 10^{-13}) \]

Using a calculator, compute the logarithm: \[ \text{pH} = -\log_{10} (6.69 \times 10^{-13}) \approx 12.2 \]

Final Answer