Question

Observe the following solutions \[ \text{I. Black coffee} \quad \text{II. 0.2M NaOH} \quad \text{III. Lemon juice} \quad \text{IV. Lime water} \quad \text{V. Human Saliva} \quad \text{VI. Tomato juice} \] The number of solutions having pH range of 1-7 and 7-14, in the above list, is respectively

• A. 1, 5
• B. 3, 3
• C. 2, 4
• D. 4, 2

Hint:

Remember, acidic solutions have a pH less than 7, and basic solutions have a pH greater than 7. Identifying the pH range helps classify the solution as acidic or basic.

Answer 1

The Correct Option is D

- Solutions with pH in the range 1-7 are acidic. - Solutions with pH in the range 7-14 are basic (alkaline). \begin{itemize} \item I. Black coffee is mildly acidic with a pH of around 5, so it falls in the 1-7 range. \item II. 0.2M NaOH is a strong base, so it falls in the 7-14 range. \item III. Lemon juice is acidic with a pH of around 2, so it falls in the 1-7 range. \item IV. Lime water is basic with a pH around 12, so it falls in the 7-14 range. \item V. Human saliva is slightly acidic with a pH around 6, so it falls in the 1-7 range. \item VI. Tomato juice is slightly acidic with a pH of around 4, so it falls in the 1-7 range. \end{itemize} Thus, the number of solutions having pH range 1-7 is 4 (Black coffee, Lemon juice, Human Saliva, Tomato juice), and the number of solutions having pH range 7-14 is 2 (0.2M NaOH, Lime water). Thus, the correct answer is option (4) 4, 2.

Answer 2

Step 1: Understanding pH Scale
The pH scale ranges from 0 to 14, where:
- pH 1-7 indicates acidic solutions.
- pH 7-14 indicates basic (alkaline) solutions.
- pH 7 is neutral.

Step 2: Analyzing Each Solution
I. Black coffee – acidic, pH around 5
II. 0.2M NaOH – strongly basic, pH above 12
III. Lemon juice – strongly acidic, pH around 2
IV. Lime water (calcium hydroxide solution) – basic, pH around 12
V. Human saliva – slightly acidic to neutral, pH around 6.5-7
VI. Tomato juice – acidic, pH around 4

Step 3: Counting Solutions in Each pH Range
- pH 1-7 (acidic): Black coffee (I), Lemon juice (III), Human saliva (V), Tomato juice (VI) → 4 solutions
- pH 7-14 (basic): 0.2M NaOH (II), Lime water (IV) → 2 solutions

Step 4: Conclusion
Hence, the number of solutions with pH 1-7 and 7-14 are 4 and 2 respectively.