Chemistry Qualitative Analysis. Cation Test

Some notes on Cation testing. 🙂

Some students have problem remember these coloured precipitates so i came up with some funny statements for students to remember these chemistry facts easier. 🙂 🙂

There are 3 coloured precipitates you have to know. Cu²+,Fe²+,Fe³+. 

I have come up with a funny statement below to remember the colours associated with the ions. Hope its blesses you! 🙂

generico brasileiro do viagra dental equipment technician resume non prescription prednisone for dogs argumentative essaya mal uso del viagra synthroid 150 mcg viagra is not working for me source go viagra and pills go site get link copd case study pharmacy creative writing essay rubric essay on my favourite cartoon tom and jerry accutane fda te rating ordering amoxicillin online from usa case study house plans essay the future language csulb university thesis office resume writing services charleston sc resume writing services cost difference between 50mg and 100mg viagra pie chart essay example diagnostic essays examples analytical research paper topics China 2-engine Balloon plane

Fly 2 Guangzhou

Ferry 3 Babies

Look at all the Caps Letters. 🙂

Cu²+ Blue ppt

Fe²+ Green (dirty green actually) ppt

Fe³+ Brown (reddish brown actually)ppt

For the white precipitates (Zn²+, Ca²+, Al³+, Pb²+), recall that ZAP are actually the amphoteric metal oxides ions. 🙂

Ca²+ forms a ppt that is insoluble in sodium hydroxide and yet forms no ppt with aqueous ammonia, hence pls test for this first. ?
If the ppt dissolves in excess sodium hydroxide, test with aq ammonia and see if the ppt dissolves in excess too. If it does, its Zn²+. (FUNNY MEMORY TIP : Z–>ZEBRA, A VERY MEEK ANIMAL SO IT KENNA ‘EATEN UP’ BY BOTH SOLUTIONS) 🙂

Both Pb²+ and Al³+ ions have the SAME reactions with sodium hydroxide and aq ammonia. Their ppt dissolves in excess sodium hydroxide but remains insoluble in excess aq ammonia. 

Irritating max right?? Keke. Nevermind, just means 1 more point to exercise our memorising muscle. 

lead cation can be further distinguished from aluminium cation by adding aqueous potassium iodide. If lead cation is present, a yellow ppt. of lead (II) iodide is formed.

I hope you will be thinking WHY aluminium iodide is not formed by adding potassium iodide meh? 

Yes!! No reaction! No ppt observed! 

In sec 3/4  syllabus, just note aluminium iodide is obtained from a reaction between metallic aluminum or aluminum hydroxide with hydrogen iodide or hydroiodic acid. OR aluminium iodide may be prepared by heating aluminium with iodine in a sealed tube or by passing iodine vapour over heated aluminium. 


Enjoy! Next week i will test the sec 3/4 chemistry students. If you receive my WA msg on this blog post link, its You! Keke. 

Leave a Reply

Your email address will not be published. Required fields are marked *