Which substance has a pH closest to 1?

Vinegar is a solution of acetic acid, which is a weak acid. The pH scale measures the concentration of hydrogen ions in a solution, with lower values indicating higher acidity. A pH of 1 is very acidic and typically indicative of strong acids. While vinegar has a pH that is more acidic than neutral (which is 7), its pH is usually around 2-3, depending on the concentration. This means it is significantly more acidic than neutral substances like water, which has a pH of 7, or baking soda, which is a basic substance with a pH around 9. Bleach, being a strong base, has a much higher pH, often greater than 12. Thus, vinegar, while not as low as 1, is the closest to that extreme acidity compared to the other substances listed.