2. Milk, pure water, lemon juice, and gastric juice were tested using a pH meter. Results are summarized in the chart below. Which substance is the most acidic?
Answer: C
Gastric juice is the most acidic substance tested.
Gastric juice has the lowest pH value among the substances tested, indicating that it is the most acidic. This aligns with the known properties of gastric juice, which contains hydrochloric acid and plays a crucial role in digestion.
A) Pure water
Pure water is neutral with a pH of 7, meaning it is neither acidic nor basic. Therefore, it does not qualify as the most acidic substance among those tested.
B) Milk
Milk has a slightly acidic pH, typically around 6.5 to 7, but it is still above the acidity level of gastric juice. Thus, milk cannot be considered the most acidic substance in this comparison.
C) Gastric juice
Gastric juice is highly acidic, generally having a pH between 1.5 and 3.5, making it the most acidic substance tested. Its composition, particularly the presence of hydrochloric acid, contributes to this low pH.
D) Lemon juice
Lemon juice is also acidic, with a pH ranging from about 2 to 3. However, it is not as acidic as gastric juice, which has a lower pH value. Therefore, lemon juice does not hold the title of the most acidic substance in this context.
Conclusion
Gastric juice is definitively the most acidic substance tested due to its significantly lower pH compared to the other options. While lemon juice is acidic, it does not reach the level of acidity found in gastric juice. Pure water and milk are neutral and only slightly acidic, respectively, further confirming that gastric juice is the correct answer.