Chemistry Ka & Kb Relationship Flashcards

Questions and Answers

What can you say about Kb tables?

They are equal to Ka

You can't find Kb from Ka

They usually don't exist (correct)

They usually exist

How do you find Kb from Ka?

Kb = (10^-14)/Ka

What is the relationship between pKa and pKb?

pKa + pKb = 14

If pKa = 10, what is the pKb of sodium phenoxide?

4 Signup and view all the answers

How do you calculate the concentration of pyridine needed to produce a solution with a pH of 8?

Check notes for the full procedure (Using Kb and pH to calculate initial conc) Signup and view all the answers

What does a 0.25M weak base solution with a pH of 9.25 indicate regarding its Kb?

Check notes for full procedure (Weak-Acid base Calculations) Signup and view all the answers

Which of the following indicates the strongest conjugate base?

pKa = 10 Signup and view all the answers

What can be said about the conjugate bases of strong acids?

Very weak bases Signup and view all the answers

What can be said about the conjugate bases of weak acids?

Weak bases Signup and view all the answers

Where can you find the diagrams of the strength of acid-base pairs?

In the notes Signup and view all the answers

Study Notes

Kb and Its Characteristics

Kb tables are not commonly available despite every acid having a conjugate base, implying a relationship between Ka and Kb.
Kb can be derived from Ka using the formula: Kb = (10^-14) / Ka.

Relationship Between pKa and pKb

The relationship is defined by the equation: pKa + pKb = 14.

Example Calculations

For sodium phenoxide with a pKa of 10:
- pKb is calculated as 14 - 10 = 4.
- Thus, Kb = 10^-4.

Concentration Calculations

To find the concentration of pyridine needed for a pH of 8:
- Convert pH to [OH-]eq.
- Use the Kb reaction and known values to calculate Kb.
A 0.25 M weak base with a pH of 9.25:
- Determine [OH-]eq from pH.
- Use the ICE table approach to calculate Kb.

Identifying Conjugate Bases

The strongest conjugate base is found from the weakest acid:
- E (pKa = 10) has the highest pKa and lowest Ka, indicating it has the strongest conjugate base.

Conjugate Bases of Acids

The conjugate bases of strong acids are very weak bases and generally incapable of acting as bases. This is due to their complete dissociation in solution.
The conjugate bases of weak acids are categorized as weak bases.

Visual Aids

Consult notes for diagrams illustrating the strength of acid-base pairs to enhance understanding.

Description

Explore the critical relationship between Ka and Kb through our interactive flashcards. Learn how to calculate Kb from Ka and understand the connection between pKa and pKb. Perfect for chemistry students aiming to solidify their understanding of acid-base concepts.