14) We define pH as pH = -log [H + ]; therefore, [H + ] = antilog (-pH). Also, w

Question

14) We define pH as pH = -log [H+]; therefore, [H+] = antilog (-pH).

Also, we know that [H+]*[OH-] = Kw = 1.0*10-14 where Kw is the ionic product of water. Use the two relations above to find out the values.

Solution

pH

[H+] M

[OH-] M

Tomato Juice

4.2

antilog (-4.2) = 6.31*10-5

(1.0*10-14)/(6.31*10-5) = 1.58*10-10

Blood Plasma

7.4

antilog (-7.4) = 3.98*10-8

(1.0*10-14)/(3.98*10-8) = 2.51*10-7

Seawater

8.2

antilog (-8.2) = 6.31*10-9

(1.0*10-14)/(6.31*10-9) = 1.58*10-6

Solution

pH

[H+] M

[OH-] M

Tomato Juice

4.2

antilog (-4.2) = 6.31*10-5

(1.0*10-14)/(6.31*10-5) = 1.58*10-10

Blood Plasma

7.4

antilog (-7.4) = 3.98*10-8

(1.0*10-14)/(3.98*10-8) = 2.51*10-7

Seawater

8.2

antilog (-8.2) = 6.31*10-9

(1.0*10-14)/(6.31*10-9) = 1.58*10-6

Explanation / Answer

14. Cakculate the H and OH concentrations of the listed solutions. OH ] M H ] M SolutionpH Tomato juice 4.2 Blood plasma 7.4 Seawater 15. State two reasons why pH maintenance is important to biological systems, and give ex- amples of how pH may affect biological reactions. 16. You have four 1,000-ml beakers filled with four different clear solutions 0.1 M NaH,Po, 0.1 M Na,HPo, 0.1 M phosphate buffer, pH 7.2 Distilled water og (3.4 Oops! You forgot to label them and they all look alike. You get the congo red and thymolph thalein from the lab and test a sample of each solution, labeling the beakers randomly as A. B, C, and D. You use congo red when HCl is added to the sample, and thymolphthalein when NaOH is added. You get the following results. Color After Color Before Addition Add Addition Colorless Red Colorless Red Colorless Red Colorless HCI NaOH HCl NaOH HCI NaOH HC NaOH Red Blue Blue Blue Red Colorless Blue Colorless What is the identity of solutions A, B, C, and D?

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