An acid is a substance that will dissociate in water to give a proton (or H+ ion) and a conjugate base. An acid is considered to be strong if dissociation nears 100%, and weak if dissociation is usually less than 1%.
In this lesson, we will learn about strong alkalis and weak alkalis.
An alkali is a soluble base that has a pH greater than 7, turns red litmus paper blue, and universal indicator solution green if it is weak and blue to purple if it is strong. But in the absence of universal indicator solution, how can we tell if an alkali is strong or weak?
In water, sodium hydroxide dissociates into a Na+ ion and a OH- ion. Since sodium hydroxide almost completely dissociates (100%), it is considered to be a strong alkali. The concentration of OH- ions in a solution containing a strong alkali will be high.
Other examples of strong alkalis include potassium hydroxide and calcium hydroxide.
These substances, when dissolved in water will turn universal indicator solution a very deep purple, and are highly corrosive.
In contrast, a weak alkali is one that does not completely dissociate in water.
A good example of a weak alkali is ammonium hydroxide (NH4OH).
In water, it does not completely dissociate into its respective ions. The concentration of OH- ions in a solution containing a weak alkali will be much lower.
These substances, when dissolved in water will turn universal indicator solution a green or light blue, and are less corrosive than strong alkalis for a given concentration.
In conclusion, a strong alkali dissociates almost completely in water to give a high concentration of hydroxide ions, whereas dissociation for a weak alkali is much less and therefore the concentration of hydroxide ions is much lower.
SUBSCRIBE to the FuseSchool YouTube channel for many more educational videos. Our teachers and animators come together to make fun & easy-to-understand videos in Chemistry, Biology, Physics, Maths & ICT.
VISIT us at www.fuseschool.org, where all of our videos are carefully organised into topics and specific orders, and to see what else we have on offer. Comment, like and share with other learners. You can both ask and answer questions, and teachers will get back to you.
These videos can be used in a flipped classroom model or as a revision aid.
Find all of our Chemistry videos here:
Find all of our Biology videos here:
Find all of our Maths videos here:
Access a deeper Learning Experience in the FuseSchool platform and app: www.fuseschool.org
Follow us: http://www.youtube.com/fuseschool
Friend us: http://www.facebook.com/fuseschool
This Open Educational Resource is free of charge, under a Creative Commons License: Attribution-NonCommercial CC BY-NC ( View License Deed: http://creativecommons.org/licenses/by-nc/4.0/ ). You are allowed to download the video for nonprofit, educational use. If you would like to modify the video, please contact us: firstname.lastname@example.org
Tagged under: Science,Chemistry,learn,Revision,GCSE,Alevels,AQA,students free online courses video science videos,student,fuseschool,global education,ict4d,acids,alkalis,strong alkalis,weak alkalis,dissociation,dissociate,conjugate base,ions
Find more lesson plans like this:Crafting Strong and Coherent Paragraphs in Business Communication
Add multiple choice quizzes, questions and browse hundreds of approved, video lesson ideas for Clip
Make YouTube one of your teaching aids - Works perfectly with lesson micro-teaching plans
1. Students enter a simple code
2. You play the video
3. The students comment
4. You review and reflect
* Whiteboard required for teacher-paced activities
Carry out a quickfire formative assessment to see what the whole class is thinking
Create interactive presentations to spark creativity in class
Student teams can create and share collaborative presentations from linked devices
Turn any public video into a live chat with questions and quizzes