Obtain 10 large test tubes clean, but may be wet. Label each test tube with the solutions to be tested. Pour about 3-mL of each solution into the appropriately labeled test tube. Using a dropper pipet, add an equal volume of cabbage indicator solution.
If necessary, stir to mix with a clean stirring rod rinse with distilled water between uses. Record the resulting color of the sample after mixed with the cabbage indicator. Compare this color with pH standards at the front of the laboratory to determine the pH of the sample.
The color may be between the pH standard colors e. For these, record the pH to 0. Do not discard the contents in these test tubes as they will be used in the next section. Plug the probe into one port on the side of the pH meter. Plug the AC adapter into the other side of the pH meter; plug the adapter into an electrical outlet. You should see a pH value reading. Note: Do not completely submerge the probe.
The handle is not waterproof. Use the same ten test tubes containing samples from Part B. Or, complete steps 1 and 2 of Part B to obtain ten samples for analysis. Insert the pH probe directly into each test tube. The probes must NOT touch the glass rim of the test tubes or the pH blub can easily be broken and the probe destroyed.
Record the pH value to 0. After each pH measurement, the probe must be thoroughly rinsed with distilled water. When you are finished making measurements, rinse the probe with distilled water.
Slide the cap onto the probe, and then screw the cap onto the storage bottle so the tip of the probe is immersed in the storage solution. Part D: Effect of Buffers on pH 1.
Obtain 4 large test tubes. Label the test tubes A, B, C, and D. Add mL of distilled water to tubes A and C. Add a 5-mL quantity of both 0. This mixture of acetic acid and sodium acetate is a buffer solution. Stir to mix completely. Using pH paper, determine the pH of the contents of each test tube A-D. Use the stirring rod to dab a small drop of the solution to be tested onto a piece of pH paper. Then compare the color obtained to the pH scale on the instructors desk to determine the pH value.
Add 3 teflon boiling chips to the water, and boil the water for five minutes on a hot plate set on medium high. This will drive off dissolved CO2 from the water which may interfere with the experiment. Allow the water to cool to room temperature. Obtain a pH meter from the instructor. Remove the rubber tip from the electrode and place the electrode in a beaker containing 10 mL of pH 7 buffer.
Soak the electrode in the buffer solution for five minutes to condition the electrode. Discard the buffer in the sink. Refer to the instructions for using the pH meter. Standardize the meter to pH 7. Student 2 4. Obtain the following items from the instructor: 1 mL volumetric flask, with stopper 2 burets, 2 buret clamps, and 2 ring stands 2 mL volumetric pipets, and pipet pumps Attach the buret clamp to the ring stand.
Clean the flask with soap and water, and rinse carefully with two mL portions of distilled water. Clean the burets with tap water, followed by two rinses with distilled water.
Then place each buret in the buret clamp on the ring stand. Clean the pipets with tap water, followed by two rinses with distilled water. Label one pipetA and the other B. Acid-Base Buffers 8. Pour mL of 0. Label the beaker. Record the concentration on line 16 of your lab report. Pour 80 mL of 0. If it is open, close the stopcock on the NaOH buret. Use a funnel to pour approximately 10 mL of 0. Remove the buret from the buret clamp and roll the buret in your hands to allow the NaOH to coat the inside of the buret.
Discard the rinse into a mL beaker through the stopcock. Return the buret to the buret clamp and close the stopcock. Now fill the buret with 0. Open the stopcock to drain the buret to 0. Discard the rinse into the sink. Repeat steps 10 and 11 for the HCl buret, using 0. The same mL beaker can be used to collect the drain. Student 1 Preparation of 0.
Record the mass of the sample to three decimal places in your notebook. Transfer the KHP sample to the mL volumetric flask, and dissolve in approximately 40 mL of boiled distilled water. Then add boiled distilled water to the flask until the bottom of the meniscus is even with the mark on the neck of the flask.
Use an eyedropper from your desk to add the last few drops of water. Stopper the flask, and turn it upside down three or four times to mix the solution totally. Transfer the KHP solution to a clean mL beaker. Label the solution as you have been instructed. Determine the concentration of the KHP solution.
Preparation of 0. Student 1 Use pipet A to transfer Record the volume on the lab report. Use a graduated cylinder to add Mix the solution thoroughly.
By using a clean stirring rod, one droplet of the hand soaps is obtained using one end of the solution and then dropped a droplet of the hand soap on one piece of pH meter.
D Buffer solution 1. Remove the rubber tip from the electrode and place the electrode in a beaker containing 10 mL of pH 7 buffer. Student 2 Acid-Base Buffers 8. Perhaps the most important reaction is the one in which an acid and base are combined, resulting in the formation of water in aqueous solution and a salt; this reaction is called neutralization.
Buffer solution plays an important role in process like neutralization. The solution must be stirred well to make sure that the mixture is mix thoroughly. Determine the concentration of the KHP solution. A total of 25ml of the following substances is pour into separate, clean, and dry beakers. Its pH values are greatly increased.
The initial pH value is 5.
Record the pH of the two solutions. The initial pH value is 5. One source of the present error may be attributed to the improperly calibrated pH meter with solution that may have been inadvertently tampered with by the chemicals added to the calibrating solutions by earlier experimenters.
By using a clean stirring rod, one droplet of the hand soaps is obtained using one end of the solution and then dropped a droplet of the hand soap on one piece of pH meter. Since HCl, HNO3, and H2SO4 are all strong acids, these substances will ionize completely and their concentrations will be too insignificant to maintain constant pH values. The meter reading shows an exact pH value of the solution probed.
Results: See Appendix 1 for all tables and graphs. Slide the cap onto the probe, and then screw the cap onto the storage bottle so the tip of the probe is immersed in the storage solution. On the other hand, a weak acid such as acetic acid, CH3COOH, only ionizes to a small extent, so the both the undissociated acid and its anion can exist in sufficient concentration in solution to maintain constant pH. Transfer the KHP sample to the mL volumetric flask, and dissolve in approximately 40 mL of boiled distilled water. The stirring rod must clean with deionized water before contact with next solution.
In this part of experiment, hand soaps are being used. The initial pH value is 5. For example it can be keep in calibration buffer solution.
Perhaps the most important reaction is the one in which an acid and base are combined, resulting in the formation of water in aqueous solution and a salt; this reaction is called neutralization. An buffer solution must contain both a weak acid and a salt of its conjugate base. This is a way to determine pH of a solution visually. Add very dilute HCl around 0. It was expected that the NaOH solution would have a 0.