Question

6) Spit contains compounds such as enzymes and ions that aid in the digestion of foods. Based on the pH of spit (7.40pH), predict the likely acid-base percentage of the major ions present in spit.

7)Bicarbonate is an important ion in human health and biology, and it is found in spit. Write an acid-base neutralization reaction that shows the production of a salt that dissociates in water to produce bicarbonate ion.

9) Based on the pH of spit (7.40), the pKa of the acid in the bicarbonate buffer system, and that spit contains 0.0250M bicarbonate, what is the concentration of the acid of bicarbonate in spit. (Hint: use the Henderson-Hasselbalch equation)

Answer 1

6. The saliva is slightly alkaline (pH 7.40). The slightly basic environment of the saliva means that it contains a high concentrartion of the bicarbonate ions. Along with this, the ions such as potassium, iodide and calcium ions are also present in higher concentration as compared to the chloride and sodium ions, which are present in lower concentrations.

Considering the molarity of the saliva as 0.1 M:

pH = -log [H+}

7.4 = -log [H+}

[H+} = 1/ 107.4 = 3.98 mmol/l = 0.0039

The acids present in the saliva are weak, hence, the HA = 0.1

Hence, {H+}/{HA} * 100 = (0.0039/0.1) * 100 = 3.9%