1 / 13

Understanding Acid-Base Equilibria: Calculating Ka and Analyzing Weak Acids

In this lesson, we will model acid-base equilibria, focusing on calculating the acid dissociation constant (Ka) for weak acids. We'll start by reviewing the pH of a given weak acid solution and derive its Ka value. Through group activities, you'll explore different acid solutions, using ICE tables to determine species concentrations. We will also address polyprotic acids and the relationship between acid strength and molecular structure. Students will learn to discuss and compare the hydronium ion concentration in various solutions, enhancing their understanding of acid-base chemistry.

zlata
Télécharger la présentation

Understanding Acid-Base Equilibria: Calculating Ka and Analyzing Weak Acids

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Catalyst: Wednesday February 5, 2014 Take out your homework Today’s Objective: -SWBAT model acid-base equilibria

  2. Review The pH of a 0.150 M solution of a weak acid is 4.10. Calculate the Ka value of the acid.

  3. Announcements • Saturday School: 10-11ish • Monday: Cold Call Quiz

  4. Photo of the day

  5. Using ICE Tables How do we know when to use an ICE table to determine pH? Consider the following two problems • Determine the pH of a solution of 0.050 M HCl • Determine the pH of a solution of 0.080 M HF

  6. Modeling Give each group a different problem Consider a solution of Weak Acid HA D H+ + A- • Determine the pH of the solution if [HA] = ? M • What species is present in the greatest concentration? • On your whiteboard, model the relative concentrations of each species HNO2 Ka = 4.0 x 10-4 HCOOH Ka= 1.77 x 10-4 HF Ka = 7.2 x 10-4

  7. Conclusion • What can we conclude about the relative concentrations of each species of a weak acid at equilibrium? • What is present in greatest quantity? • What is present in the lowest quantity?

  8. Discussion Question • Consider the following two solutions • HNO2: pH = 3.5 • HCl: pH = 3.5 Which solution has the greater concentration of hydronium ion in solution?

  9. Lecture • Kw = Ka * Kb

  10. Table Talk • Calculate the Ka for the ammonium ion (Kb = 1.8 x 10-5)

  11. Table Talk • Consider the following two acids and their ionization constants: HCOOH Ka = 1.7 x 10-4 HCN Ka = 4.9 x 10-10 Which conjugate base (HCOO- or CN-) is stronger? Explain.

  12. Lecture • Polyprotic acids: Acid that can donate more than one H+ • Calculations of Ka are more complicated because you need to take into account all potential ionizations • We’ll focus just on monoprotic acids • Acid Strength based on structure • Increasing size and EN leads to an increase in acid strength • Essentially, if molecule can ionize easier, it is a stronger acid • Increasing size and EN weakens bond

  13. Lecture

More Related