Transcribed TextTranscribed Text

Experiment 5 Acid-Base Titration A titration is a process used to determine the volume of a solution needed to react with a given amount of another substance. In this experiment, you will titrate hydrochloric acid solution, HCI, with a basic sodium hydroxide solution, NaOH. The concentration of the NaOH solution is given and you will determine the unknown concentration of the HCI. Hydrogen ions from the HCI react with hydroxide ions from the NaOH in a one-to-one ratio to produce water in the overall reaction: When an HCI solution is titrated with an NaOH solution, the pH of the acidic solution is initially low. As base is added, the change in pH is quite gradual until close to the equivalence point, when equimolar amounts of acid and base have been mixed. Near the equivalence point, the pH increases very rapidly, as shown in Figure 1. The change in pH then becomes more gradual again, before leveling off with the addition of excess base. In this experiment, you will use a computer to monitor pH as you titrate. The region of most rapid pH change will then be used to determine the equivalence point. The volume of NaOH titrant used at the equivalence point will be used to determine the molarity of the HCI. Acid-Base Titration 12 10 8 6 4 2 2 4 6 Volume NaOH (mL) Figure 1 OBJECTIVES Use a pH Sensor to monitor changes in pH as sodium hydroxide solution is added to a hydrochloric acid solution. Plot a graph of pH vs. volume of sodium hydroxide solution added. Use the graph to determine the equivalence point of the titration. Use the results to calculate the concentration of the hydrochloric acid solution. MATERIALS computer magnetic stirrer (if available) stirring bar wash bottle distilled water HCI solution pH Sensor unknown concentration ring stand ~0.1 M NaOH solution 1 utility clamp pipet bulb 50 mL buret 10 mL pipet 250 mL beaker 2nd 250 mL beaker 2nd utility clamp O CP PROCEDURE 1. Obtain and wear goggles. 2. Add 50 mL of distilled water to a 250 mL beaker. Use a pipet bulb to pipet 10.0 mL of the HCI solution into the distilled water in the 250 mL beaker. CAUTION: Handle the hydrochloric acid with care. It can cause painful burns if it touches the skin. 3. Place the beaker on a magnetic stirrer and add a stirring bar. 4. Use a utility clamp to suspend a pH Sensor on a ring stand as shown here. Position the pH Sensor in the HCI solution and adjust its position so it will not be struck by the stirring bar. Turn on the magnetic stirrer, and adjust it to a medium stirring rate (with no splashing of solution). 5. Obtain approximately 60 mL of ~0.1 M NaOH solution in a 250 mL beaker. Obtain a 50 mL buret and rinse the buret with a few mL of the ~0.1 M NaOH solution. Use a utility clamp to attach the buret to the ring stand as shown here. Fill the buret a little above the 0.00 mL level of the buret with ~0.1 M NaOH solution. Drain a small amount of NaOH solution into the beaker so it fills the buret tip and leaves the NaOH at the 0.00 mL level of the buret. Record the precise concentration of the NaOH solution in your data table. Dispose of the waste solution from this step as directed by your teacher. CAUTION: Sodium hydroxide solution is caustic. Avoid spilling it on your skin or clothing. 6. Continue adding NaOH solution in increments that raise the pH by about 0.15 units and enter the buret reading after each increment. Proceed in this manner until the pH is 3.5. 7. When a pH value of approximately 3.5 is reached, change to a one-drop increment. Enter a new buret reading after each increment. Note: It is important that all increment volumes in this part of the titration be equal; that is, one-drop increments. 8. After a pH value of approximately 10 is reached, again add larger increments that raise the pH by about 0.15 pH units, and enter the buret level after each increment. 9. Continue adding NaOH solution until the pH value remains constant. DATA TABLE Trial 1 Trial 2 Concentration of NaOH 0.1 M 0.1 M NaOH volume added before the largest pH 24.5 mL 24.3 mL NaOH volume added after the largest pH increase 25.5 mL 25.6 mL Use the information in the data table above, determine and fill in the box below: Trial 1 Trial 2 Volume of NaOH added at equivalence point (Hint: average of NaOH volume before and after largest pH change) Moles NaOH (Hint: Use molarity equation to determine the mole of NaOH, molarity and volume of NaOH at equivalence points are in the data table.) Moles HCI (Hint: stoichiometric ratio of HCI and NaOH is 1 to 1) Molarity of HCI (Hint: volume of HCI used in this experiment is 10 mL) Average [HCI]

Solution PreviewSolution Preview

This material may consist of step-by-step explanations on how to solve a problem or examples of proper writing, including the use of citations, references, bibliographies, and formatting. This material is made available for the sole purpose of studying and learning - misuse is strictly forbidden.

    By purchasing this solution you'll be able to access the following files:
    Solution1.pdf and Solution2.docx.

    for this solution

    PayPal, G Pay, ApplePay, Amazon Pay, and all major credit cards accepted.

    Find A Tutor

    View available Chemistry - Other Tutors

    Get College Homework Help.

    Are you sure you don't want to upload any files?

    Fast tutor response requires as much info as possible.

    Upload a file
    Continue without uploading

    We couldn't find that subject.
    Please select the best match from the list below.

    We'll send you an email right away. If it's not in your inbox, check your spam folder.

    • 1
    • 2
    • 3
    Live Chats