Introduction
In this lesson we will look at the different ACID-BASE theories as well as CONJUGATE ACID- BASE PAIRS.
All around you there are chemical reactions taking place. Green plants are photosynthesizing, car engines are relying on the reaction between petrol and air and your body is performing many complex reactions.
What are ACID -BASE reactions?
The Bronsted-Lowry model defines acids and bases in terms of their ability to donate or accept protons.
- A Bronsted-Lowry acid is a substance that gives away protons (hydrogen cations H+), and is therefore called a proton donor.
- A Bronsted-Lowry base is a substance that takes up protons (hydrogen cations H+), and is therefore called a proton acceptor.
Consider the following reaction:
HCl (aq)+NH3(aq)→NH+4(aq)+Cl−(aq)
We highlight the chlorine and the nitrogen so that we can follow what happens to these two elements as they react. We do not highlight the hydrogen atoms as we are interested in how these change. This colour coding is simply to help you identify the parts of the reaction and does not represent any specific property of these elements.
HCl (aq)+NH3(aq)→NH+4(aq)+Cl−(aq)
In order to decide which substance is a proton donor and which is a proton acceptor, we need to look at what happens to each reactant. The reaction can be broken down as follows:
HCl (aq)→Cl−(aq)
and
NH3(aq)→NH+4(aq)
From these reactions, it is clear that HCl is a proton donor and is therefore an acid, and that NH3 is a proton acceptor and is therefore a base.
Conjugate Acid-Base Pair
NOTE:Use the links below to gain a better understanding of today's lesson.
https://intl.siyavula.com/read/science/grade-11/types-of-reactions/13-types-of-reactions-01
https://phet.colorado.edu/sims/html/ph-scale/latest/ph-scale_en.html
Task
Task 2:
Date: 5 September 2021
Due Date: 15 September 2021
Marks: 25
Instructions: This is an individual assessment.
Read the questions carefully and answer the following questions.
Use the links provided to assist you in answering the questions below.
Question 1
How do acids and bases differ in:
1.1 How they feel? (2)
1.2 How they taste? (2)
Question 2
Give the definition of an acid and a base according to:
2.1 Arrhenius’ theory (3)
2.2 The Brønsted - Lowry theory (3)
Question 3
Identify the conjugate acid-base pairs in the following reactions:
3.1 CH3COO- + H2O ⇄ CH3COOH + OH- (2)
3.2 NH4+ + H2O ⇄ NH3 + H3O+ (2)
3.3 H2SO4 + H2O ⇄ HSO4- + H3O+ (2)
3.4 H2SO4 + Cl- ⇄ HSO4- + HCl (2)
Question 4
When hydrogen fluoride reacts with water, it ionizes as shown in the balanced equation below:
HF(ℓ)+H2O(ℓ) → H3O+ (aq)+ F−(aq)
4.1 What is a Brønsted-Lowry acid? (2)
A - a substance that produces H3O+ ions when it dissolves in water.
B - an H+ ion acceptor.
C - a proton donor.
D - a substance that produces hydroxide ions when it dissolves in water.
Total: 25
Process
Step 1
Thoroughly read through the introduction content on the "Introduction" Page to understand the ACID -BASE reaction concept.
Make use of the links provided in the introduction page by clicking on each link and watching attentively.
Step 2
Go to "Task" page and read the instructions carefully.Read through the questions before answering.
Step 3
Go to "Evaluation" page and see how your task will be evaluated.
Step 4
Answer all task questions.Once you have completed your task,submit it to thanzi90@gmail.com
NB:Task is due on the 12th October 2021.No late tasks will be accepted!!!
Step 5
Go to "Conclusion" page.Read the content provided and click on the link provided which concludes the concept of Acid -Base reactions.
Evaluation
Acid -Base Evaluation
NB: You will be assessed according to the mark allocations in the task per question.
Extra ( 5) marks can be obtained by learners who are able to do the following from the Task.
| Score | Poor
1 -2 |
Fair
3 -4 |
Good
5 |
| Identifying Acids - Bases
|
Poor
|
Fair
|
Good
|
| Defining Acids -Base theories
|
Poor
|
Fair
|
Good
|
| Reaction involving Conjugate acids & bases
|
Poor
Student is unable to identify the Conjugate Acid -Base pairs. |
Fair
Student partially identified the Conjugate Acid -Base pairs. |
Good
|
Conclusion
WELL DONE !!!
In this lesson we have learned the following about of Acid - Base reactions:
The Bronsted - Lowry model defines acids and bases in terms of their ability to donate or accept protons.
- A Bronsted-Lowry acid is a substance that gives away protons (hydrogen cations H+), and is therefore called a proton donor.
- A Bronsted-Lowry base is a substance that takes up protons (hydrogen cations H+), and is therefore called a proton acceptor.
- A conjugate acid-base pair refers to two compounds in a reaction (one reactant and one product) that transform or change into the other through the loss or gain of a proton.
Our next class will focus on Amphiprotic Substances. Use the link below in preparation for our next class.
Credits
I would like to Thank Mr Moyo,who inspired me to make this lesson.
I acknowledge all the websites I have used in creating this lesson.
All the attached links have helped me to make this lesson a success.
https://www.expii.com/t/conjugate-acid-base-pairs-overview-examples-8458
https://www.expii.com/t/bronsted-lowry-acids-and-bases-definition-examples-11125
https://intl.siyavula.com/read/science/grade-11/types-of-reactions/13-types-of-reactions-04
https://phet.colorado.edu/en/simulations/acid-base-solutions