Correct Answer: 5.5
Subject: chemistry
Explanation: • <b>Key Fact</b> Tooth decay begins when the pH of the mouth is lower than 5.5. • <b>Supporting Detail</b> Bacteria in the mouth produce acids by degrading sugar and food particles. • <b>Related Concept</b> Tooth enamel, made of calcium phosphate, gets corroded in an acidic environment below 5.5. • <b>Why wrong options are wrong</b> 7.0 is neutral, and 1.5 is the pH of gastric juice in the stomach. • <b>Exam Trick</b> Use basic toothpastes (pH ~9) to neutralize this acid and prevent decay. • <b>Additional Info</b> Acid rain is defined when rainwater pH is below 5.6.
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