Which of the following has a neutral pH of 7?

Pure water is commonly recognized as having a neutral pH of 7. This neutrality stems from the balance of hydrogen ions (H+) and hydroxide ions (OH-) present in water; at this pH level, both ions are equal in concentration. When substances dissolve in water, they can either increase the concentration of H+ ions, resulting in a more acidic solution (with a pH less than 7), or increase the concentration of OH- ions, leading to a basic solution (with a pH greater than 7). Pure water, being free of impurities or additional ions, maintains this balance.

In contrast, saltwater typically has a slightly elevated pH due to dissolved salts, which can alter the hydrogen ion concentration, often making it slightly basic. Vinegar is an acidic solution primarily composed of acetic acid, resulting in a significantly lower pH than 7. Distilled spirits, depending on their composition, can have varying pH levels, but they are generally not neutral either, usually presenting a pH that is lower than 7 due to the presence of ethanol and other organic compounds. Thus, pure water stands out as the only option with a true neutral pH of 7.