Final answer:
To determine which aqueous solution has the lowest pH, assess the concentration of hydronium ions—higher concentrations mean a lower pH. A pH meter can be used to measure pH directly, while calculations involving negative logarithms of ion concentrations can be used for weak acids or bases.
Step-by-step explanation:
Determining the Lowest pH in Aqueous Solutions
To determine which aqueous solution has the lowest pH, we must understand pH and pOH. The pH is a measure of the acidity of a solution, with lower pH values indicating more acidic solutions. Solutions with a higher concentration of hydronium ions (H3O+) than pure water are acidic and will have a pH lower than 7. The pH can be determined using a pH meter, or by calculating it using the negative logarithm of the hydronium ion concentration. In comparative terms, the solution with the highest hydronium ion concentration will have the lowest pH. Moreover, the use of pH indicators, like phenolphthalein, can provide an estimation of pH as they change color at certain pH values.
For weak acids or bases, the pH can be calculated by first finding the pOH for bases or directly finding the pH for acids and applying the formula pH + pOH = 14. Strong acids will have very low pH values due to high H3O+ concentrations, and these can be dangerous because they can corrode materials and harm living tissues.