Question

Observe the following solutions: \[ \text{I. Black coffee} \quad \text{II. 0.2M NaOH} \quad \text{III. Lemon juice} \] \[ \text{IV. Lime water} \quad \text{V. Human Saliva} \quad \text{VI. Tomato juice} \] The number of solutions with pH less than 7 is

• A. 2
• B. 5
• C. 4
• D. 3

Hint:

Solutions with pH less than 7 are acidic. Black coffee, lemon juice, human saliva, and tomato juice are examples of such solutions.

Answer 1

The Correct Option is C

pH is a measure of the acidity or basicity of a solution. A pH value of 7 indicates a neutral solution. Solutions with pH less than 7 are acidic, while those with pH greater than 7 are basic. Let's analyze the pH of each solution: - I. Black coffee – Black coffee is mildly acidic with a pH between 5 and 6. - II. 0.2M NaOH – Sodium hydroxide is a strong base with a pH greater than 7 (around 13). - III. Lemon juice – Lemon juice is acidic with a pH around 2 to 3. - IV. Lime water – Lime water is slightly basic with a pH around 12. - V. Human Saliva – Human saliva is slightly acidic with a pH around 6.5. - VI. Tomato juice – Tomato juice is acidic with a pH around 4 to 5. Thus, the solutions with pH less than 7 are: - Black coffee (acidic) - Lemon juice (acidic) - Human Saliva (slightly acidic) - Tomato juice (acidic) Therefore, the number of solutions with pH less than 7 is 4. Thus, the correct answer is \( \boxed{4} \).