Brønsted–Lowry Acid & Bases
Dr. Davinder Bhachu
Teacher
Contents
Introduction to Brønsted–Lowry Acids and Bases
Key Definitions
Brønsted–Lowry Acid: A substance that donates a proton .
Brønsted–Lowry Base: A substance that accepts a proton .
Think of acids as "proton donors" and bases as "proton acceptors".
Acid and Bases Explainer Video
Proton Transfer
In acid–base reactions, a proton is transferred from the acid to the base.
Example:
donates a proton acid
accepts a proton base
Conjugate Acid-Base Pairs
Acid–base reactions involve two pairs of species that differ by one proton . They can be interconverted by transfer of a proton.
Species | Acts As | Conjugate Pair |
Acid (donates ) | (conjugate base) | |
Base (accepts ) | (conjugate acid) |
General rule:
So:
Acid Conjugate base (loses )
Base Conjugate acid (gains )
No answer provided.
Strong vs Weak Acids/Bases
Type | Definition | Example | Dissociation |
Strong Acid | Fully dissociates in water | , | One-way arrow |
Weak Acid | Partially dissociates in water | Reversible arrow | |
Strong Base | Fully dissociates in water | ||
Weak Base | Partially dissociates in water |
Acid-Base Equilibria and Reversibility
In reactions involving weak acids or bases, equilibrium is established
Example:
Acid and conjugate bases are found on opposite sides of the equilibrium.
Exam Tips
Always identify both acid–base pairs in equilibrium questions.
Look for proton transfer to determine acids and bases.
Clearly label conjugate acid–base pairs.
No answer provided.
Worked Examples
Example 1: Identifying Acid and Base
Reaction:
Answer:
donates acid
accepts base
Conjugate pairs:
No answer provided.
Example 2: Writing Conjugate Pairs
Question: Write the conjugate acid of and the conjugate base of .
Answer:
Conjugate acid of
Conjugate base of
No answer provided.
Example 3: Equilibrium Reaction
Reaction:
Question: Identify the acid-base pairs in this equilibrium
Answer:
donates acid
accepts base
Conjugate acid-base pairs:
No answer provided.
Quick Recap Table
Term | Definition |
Brønsted–Lowry Acid | Proton donor |
Brønsted–Lowry Base | Proton acceptor |
Conjugate Acid | Base that has accepted an |
Conjugate Base | Acid that has lost an |
Strong Acid/Base | Fully dissociates in water |
Weak Acid/Base | Partially dissociates in water |
No answer provided.
Practice Questions
Question 1
Identify the Brønsted–Lowry acid and base:
Reaction:
Answer:
= acid (donates )
= base (accepts )
Conjugate pairs:
Question 2
Write the conjugate base of:
a)
b)
a)
b)
Question 3
Classify each as strong or weak acids:
a)
b)
a) Strong acid (fully dissociates)
b) Weak acid (partially dissociates)