bonds are formed, A buffer is a chemical that resists lare or dramatic changes i
ID: 194917 • Letter: B
Question
bonds are formed, A buffer is a chemical that resists lare or dramatic changes in pH: a solution to which a buffer has been added is called a bafered solution. When acid is added so a baffered solution, the bufter binds the added hydrogen ions and removes them from the solution. Simlarly, when a base is added to a buffeeed solution, the baffer releases hydrogen ons ineo the solution. Both effects minimine pH changes that otherwise would oocur in the solution if the buffer were not present Exercise 2-2 Buffers MATERIALS Well plates Stiming rods Dropping ppenes Q.1M hydrochloric acid Bleed solton Procedure 1 Testing Buffered Solutions Distilled water 0.1M NaOH pH paper In this experiment you will examine the efects of adding an acid or a base to buffered solutions and nonbuffered solutions, You will use distilled water as your monbuffered solution, and your instructor will choose an appeopriate baffered solution fo you to use. Sality eses and gloves 1 Obtain a we'll plate, and number four wells 1, 2, 3, and 4. 2 Fill wells 1 and 2 about hald-full of distilled water Measure the pH of the re required 3 Fill wells 3 and 4 about hals-full of buffered solution. Measure the pH of the buffered solution, and recoed that value 4 Add two drops of 0.IM HCl to wells 1 and 3. Stir the solutions with a stirring rod (or a toothpick), and measure the 5 Add two drops of 0.1M NaOH (a base) to ditilled water, and record that value in Table 2.3 ("pH of Initial Solution in Table 2.3 ("pH of Initial Soluticn" pH of each well. Record the pH in Table 2.3("pH after the pH in Table 2.3 ("plH after") wells 2 and 4. Stir the solutions, and mesure the plt of each well, Record ABLE 2.3 Buffered and Nonbuffered Solutions Well Contents PH of Initial Solution pH after Adding Acid or Base 1Water and HC 2 Water and NaOH 3Buffer and HCI 4 Buffer and Na0H 6 Interpret your results. What effect did the buffer have on the pH changes you saw? 38 I Exploring Anatomy & Physiology in the Laboratory: Core ConceptsExplanation / Answer
1. Water + HCl
pH = 4
If you add acid, pH will decrease.
If you add base, pH will increase.
2. Water + NaOH
pH = 10
If you add acid, pH will decrease.
If you add base, pH will increase.
3. Buffer + HCl
pH = 5.5
If you add slight amounts of acid or base. No change in pH.
4. Buffer + NaOH
pH = 10.5
If you add slight amounts of acid or base. No change in pH.
Buffers resist change in pH.
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