Acidity and Alkalinity

In this experiment you will be testing the acidity and alkalinity of many common substances. We have discussed acids and bases already in lecture and I recommend you review pages 191 - 194 in your textbook. We have not discussed the concept of pH, but the introduction to the laboratory experiment provides a simple introduction to the concept. Our textbook introduces pH on page 518 - 524.

PART ONE: Acidity and Alkalinity of the Ingredients in Commercial Products

This is fairly straightforward with the possible exception of trying to decipher names and whether a substance is an acid or a base.

In this portion of the laboratory you will read the product labels of several household chemicals and classify the ingredients as acidic, basic or neutral.

PART TWO: pH of Common Household Substances

In this part you will prepare solutions of several common substances found at home to measure the pH. You will dissolve a given amount of each liquid or solid in 50 mLs of distilled water before using a pH meter to measure the pH of the solution. The amounts of each substance you are to measure is provided adjacent to the substance in the list of Chemical Needed on page 5 - 4.

Here is a general description of the procedure you will follow.

	Solids should be weighed out using the analytical balance in the laboratory. Remember to weigh solids into the plastic weighing dish, not directly on the balance. Sometimes solids will get spilled during transfer. PLEASE clean up after you use the balance. Most of the solids are 1.00 g
	Use a calibrated plastic pipet to measure the liquids.
	Transfer the substance to a 100 mL beaker
	Dilute the sample by adding 50 mLs of water.
	After preparing the solution you are ready to measure its pH. You can see the OSU pH meter being held in the left hand of our assistant. Remove the cap on the end of the electrode, and rinse the electrode with distilled water. Wipe excess water off using a KIM wipe (see the small green and white box next to the beaker.) Notes this is a QuickTime movie. I think most browsers can play QuickTime movies. Let me know if you have a problem.)
	Insert the pH electrode into the solution and be sure to avoid touching the bottom or sides of the beaker. Swirl the electrode in the solution.
	On the top of the pH meter is an ON/OFF switch. Flip the switch to ON.
	Record the pH of the solution on the Results page. Be sure to give the pH meter reading a moment to settle down so the value is not fluctuating too much. Acidic solution will have a pH less than 7. The lower the pH value the higher the concentration of hydrogen ion, H+(aq). Remember to rinse the electrode with distilled water after each measurement.
	Basic solutions will have a pH greater than 7. The higher the pH value the higher the concentration of hydroxide ion, OH-(aq). Remember to rinse the electrode with distilled water after each measurement.
	After you have measured the pH of all of the samples be sure to turn the pH meter ON/OFF switch to the OFF position.