Question

Which of the following fluid has \(\mathrm{pH}<7\):

• A. Egg white
• B. Sea water
• C. Human blood
• D. Human saliva

Hint:

For pH of biological fluids:

- Blood, egg white, sea water are typically basic (pH>7).

- Saliva can be slightly acidic (pH ~6.2–7.6).

- Check typical pH ranges for accuracy.

Answer 1

The Correct Option is D

The pH of a fluid indicates its acidity or alkalinity. A pH $<$ 7 is acidic, pH = 7 is neutral, and pH \(>\) 7 is basic. We evaluate the typical pH of each fluid.
Step 1: Typical pH values 
- (A) Egg white: pH ~7.6–9.2 (basic, increases with age due to \({CO2}\) loss). 
- (B) Sea water: pH ~8.0–8.4 (basic, due to dissolved carbonates). 
- (C) Human blood: pH ~7.35–7.45 (slightly basic, tightly regulated). 
- (D) Human saliva: pH ~6.2–7.6, often slightly acidic (e.g., ~6.7) due to bacterial activity and food residues. 
Step 2: Identify pH $<$ 7 
Only human saliva can have a pH below 7, especially after meals or due to oral bacteria. 
Step 3: Conclusion 
Human saliva is the fluid with \(\mathrm{pH}<7\), matching option (D).