Question

The pH of saliva is normally in the range of 6.4 to 7.0. However, when a person is ill, the person's saliva becomes more acidic.

(a) When Marco is sick, he tests the pH of his saliva and finds that it is 5.5. What is the hydrogen ion concentration of his saliva? (Round your answer to seven decimal places.

(b) Will the hydrogen ion concentration in Marco's saliva increase or decrease as he gets better

(c) After Marco recovers, he tests the pH of his saliva, and it is 6.7. Was the saliva more acidic or less acidic when he was sick?

Answer 1

pH = -log [H⁺]

a) at pH = 5.5,

[H⁺] = 10^-5.5 = 3.16 x 10^-6 M

or, [H⁺] = 0.0000032 M

b) Since the pH of saliva is normally on the range 6.4 to 7.0, the pH of saliva should increase when he gets better.

pH increases as H⁺ concentration decreases. So, hydrogen ion concentration in the saliva should decrease as he gets better.

c) After recovering, pH inreased to 6.7. Lower the pH, greater the acidity.

Since, pH increases, acidity should decrease, after recovery.

Hence, saliva was more acidic, when he was sick.