QuestionQuestion

Transcribed TextTranscribed Text

8. Use Excel on the computer to graph pH values, along the y-axis, versus the volume of NaOH added, along the x-axis. Note the volume where a steep rise in pH occurs for the second trial. 9. Second Trial: Repeat the titration, partners should switch roles so each person does a titra- tion. Data Trial 1 Trial 2 Volume of NaOH at the equivalence point Volume of NaOH at half the equivalence point pH at half the equivalence point pK, at half the equivalence point Dissociation Constant, K, 10-PH Part 2. The Dissociation Constant of Acetic Acid CH,COOH (aq) = __HH][CH3COO` acetic conjugate conjugate acid acid base 1. Recalibrate the pH meters using the standard solutions of pH = 7 and 4. 2. Rinse the electrodes in DI water. Blot excess water off the outside of the electrodes with a Kimwipe. Be careful not to damage the electrodes. 285 ACID IONIZATION CONSTANTS 3. 4. Place 10 mL 1.0 M acetic acid (HA) into a 50 mL beaker. Measure and record the pH. Calculate the dissociation constant of acetic acid. Solution: 10.0 mL 1.0 M HA Observed pH 10- ptt Hydrogen ion concentration, [H+], from pH 1- - X Acetate ion concentration, [A-], at equilibrium same Acetic acid concentration, [HA], at equilibrium eq. Dissociation Constant, K2 Q 5. Add 25.0 mL of 1.0 M sodium acetate (NaA) to the 10.0 mL of 1.0 M acetic acid, and mix well. Measure the pH of this solution. Calculate the H+, A-, HA concentrations in the solu- tion and the dissociation constant. Save the solution for the next step. Solution: 25.0 mL 1.0 M NaA + 10.0 mL 1.0 M HA Observed pH 5.05 Hydrogen ion concentration, [H+], from pH Total Volume Acetate ion concentration, [A-], at equilibrium Acetic acid concentration, [HA], at equilibrium Dissociation Constant, K, 6. In a 100 mL beaker, thoroughly mix 5.0 mL of 1.0 M sodium acetate with 30.0 mL of 1.0 M acetic acid. Measure and record the pH. Calculate the H+, A-, HA concentrations in the 286 ACID-BASE EQUILIBRIA: DETERMINATION OF ACID IONIZATION CONSTANTS solution and the dissociation constant. Solution: 5.0 mL 1.0 M NaA + 30.0 mL 1.0MHA Observed pH 3.81 [H+] at equilibrium (from pH) Total Volume [A-] at equilibrium [HA] at equilibrium Ka 7. For the above solutions calculate the pH using the accepted value of the acetic acid dissocia- tion constant, K2 = 1.76 X 10-5, and compare it to the measured pH in steps 5 and 6. Solutions Measured pH Calculated pH % Error 25.0 mL 1.0 M NaA + 10.0 mL 1.0 M HA 5.05 5.0 mL 1.0 M NaA + 30.0 mL 1.0 M HA 3.81 for M CONSTANTS fered Solutions Part 3. Buffering Capacity: Addition of Strong Acid and Strong Base to Buffered and Unbuf- 1. Use a 50 mL beaker for each of the following solutions. Measure and record the pH. Unbuffered Solution Measured pH Calculated pH / 30 mL DI water 5.75 2 30 mL DI water + 2 mL 1.0 M HCI 1.48 3 30 mL DI water + 2 mL 1.0 M NaOH 11.82 2. Use a 150 mL beaker to make the NaA/HA buffer solution. Measure and record the pH. two Measure 30 mL of this buffer solution and place it in 50 mL beakers for the next solutions. Measure and record the pH. Buffer Solution Measured pH Calculated pH 30 mL 1.0 M NaA + 30.0 mL 1.0 M HA 4 44.40 5 / 30 mL buffer + 2 mL 1.0 M HCI 4.32 6 J 30 mL buffer + 2 mL 1.0 M NaOH 4.56 3. What is the increase in pH after the strong acid was added to the buffer solution, relative to the pH of the buffer solution? What is the increase in pH when the strong acid was added resist DI water, relative to the pH of pure DI water? Does this show that buffer solutions to a change in pH when a small amount of a strong acid or base is added to the solution?

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.

    $35.00 for this solution

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

    Find A Tutor

    View available General Chemistry 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.

    Decision:
    Upload a file
    Continue without uploading

    SUBMIT YOUR HOMEWORK
    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