Acids Bases And Salts

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 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 , matching option (D).