Acid Base Electrolyte Lab
Biol 2402 Anatomy and Physiology II
Dr. Weis

Refer to your textbook, lecture notes, and class notes

I. Water molecules can dissociate and ionize when the hydrogen atom shared by two water molecules shifts its protons from one molecule to the other.
The equation follows: H2O + H2O <=====> H3O + OH-
By convention, the dissociation of water is written as follows: H2O <====> H+ + OH-

Terminology

• H+ hydrogen ion
• OH- hydroxide ion
• H3O+ hydronium ion

At room temperature, the pure water dissociation is low and results in small but equal concentrations of hydrogen ion and hydroxyide ion. At equilibrium, the concentration of H+ is 10 to -7 M and the concentration of OH- is also 10 to the -7 M.

Experiment and Activities

IA. Measure the pH of tap water, distilled [dH2O] water, and aquarium/pond water at room temperature using a pH meter and pH paper. Record your values

IB. Convert the one of the pH values above to decimal notation : _____________________________________

IC. Convert this decimal notation to scientific notation: _____________________________________________

ID. Name the fluid compartments of the body and their primary cation, anion, and pH.

II. Some substances when dissolved in water have the ability to change the equilibrium of the solution by adding more H+ or OH- or taking up H+ or OH- and thus affecting the final pH value.

Terminology: Define the following terms and give an example of each

III. Explain these reactions

A. HCl -----> H + + Cl-

B. NaOH -----> Na+ + OH-

C. NH3+ <=====> NH4+

D. Fill in the following reaction:
CO2 + H2O <=====> __________________ <=====> ______________ + _______________

and explain the importance of this equation.

IV. Measure the pH of the various solutions using the pH meter and pH paper. Determine if they are acidic or basic based on a neutral pH of water at 7.0 m/l.

Create a pH scale using your results for the above solutions. Start with pH = 0 and go to pH = 14

For any pH between 6 and 8, use the narrow range pH paper to determine decimal placing.
That is 6 could be 6.0 or 6.5, etc. Record your new results next to the original results for your pH paper.

How well did the pH meter correlate with the pH paper? Why or Why not?

V. Antacids are widely used to relieve the effects of heartburn and acid indigestion. This condition is often caused by excess production of HCl by the parietal cells in of the gastric mucosa in response to overstiumlation by ACh, Histamine, gastrin as well as overeating or consumtion of irritating foods. Antacids are designed to neutralize excess acids. However, if the pH of the gastric juices rises too high, the digestiive process is inhibited because pepsinogen can not be actived to pepsin to begin protein chemical digestion when the pH rises above 4.
Determining the neutralization capacity of antacids is important in that only the excess acids should be neutralized.
The following experiment will allow you to determine this effect.

1) Label 4, 250 ml Ehrlenmeyer flasks: Control. Tums, Rolaids, Alka-Seltzer

2) Add 50 ml of a 0.3M HCl solution to each of the four Flasks

3) Using a mortar and pestel, crush each tablet and place the powder in their respective flasks.
Remember: The control flask will not have any antacid added.

4) Measure the pH of all four flasks and record this in the initial pH

5) Set the flasks aside, swirling them periodically until the antacid tablets have fully dissolved.

6) Record the pH of all four flasks again as the antacid dissolved pH column

7) Wait 10 minutes. Re-record the pH of all four flasks and record your results in the final pH column.

Give the major ingredients for each antacid:

Which antacid controled excess acid better? Why ?

VI. Observe the following models or slides, identify the major parts, and explain the importance of these systems in the acid base balance. Explain in more detail specific structures mentioned in controling acid / base / electrolyte / fluid balance.

A. Respiratory models

1) Pulmonary ventilation control

2) Respiratory membrane histology

B. Renal models

1) Nephron parts

2) Urine pH vs. Blood pH

C. Brain models

1) Cortex

2) Brainstem

D. Blood slides

1) Plasma

2) RBC

VII. Refer to your Marieb Lab book under the Respiratory Lab for the following experiments and set up. Record your results in your lab book. Be able to explain these results on future tests.

A. Demonstrating the reaction of Carbon Dioxide in exhaled air and water

B. Observing the operation of standard buffers

C. Exploring the operation of the carbonic acid buffer system

VIII. Name the three chemical buffers in the body, their components, location, pH vs pK and resulting effectiveness

1)

2)

3)

IX. On a biochemical profile, the normal laboratory values are as follows

Given these normal values, what range of urinary pH can be achieved and why?

X. Problems with Acid / Base / Electrolyte Balance

Define and explain the following terms, give an example for a cause and the possible correction (compensation):

Reference Web Sites:

http://www.physiologyeducation.org/materials/simres.html#download

http://www.acid-base.com/

http://lrs.ed.uiuc.edu/students/mihyewon/chemlab_methods.html