Final answer:
Among ammonia, blood, lemon juice, and vinegar, the substance with a pH closest to 7 is blood, which has a slightly basic pH of 7.4.
Step-by-step explanation:
The substance that has a pH closest to 7 among the options provided in the question is blood. pH is a scale that measures how acidic or basic a substance is. Pure water, with a pH of 7, is considered neutral. Substances with a pH less than 7 are acidic, and substances with a pH greater than 7 are basic (alkaline). According to the information provided:
- Human blood has a pH of 7.4, making it slightly basic and the closest to neutral among the options mentioned.
- Household ammonia has a pH ranging from 10.5 to 11.5, making it a basic substance.
- Lemon juice and vinegar are both acidic, typically ranging around a pH of 2.5 to 3.5 for lemon juice, and similar acidity for vinegar.
Based on the pH values provided, human blood (pH 7.4) is the substance closest to neutral and therefore the closest to a pH of 7.