2022 NECO Exam Chemistry Practical Qualitative Analysis Review

 

   In this qualitative analysis, we are going to review the possible qualitative analysis practical exam questions you are likely to expect in the coming NECO examination. You are expected to analyse the ions in the following compounds

·         Zinc trioxocarbonate IV (labelled X_n ) watch video 1

·         Aluminium chloride  ( labelled Y_n ) watch video 2

The reagents for the qualitative analysis of these compounds include

·         Dilute sodium hydroxide solution

·         Dilute aqueous ammonia

·         Dilute hydrochloric acid

·         Distilled water

·         Red and blue litmus paper

·         Barium chloride

·         Phenolphthalein

·         Calcium hydroxide

·         Methyl orange

·         One boiling tube

·         Filtration apparatus

·         Source of  heat

s/n	Test	Observation	Inference
A(I)	X + dilute HCl, divide into two portions	Effervescence, odourless, colourless gas, turns blue litmus red, turns Ca(OH)2 milky	CO2 gas confirmed, CO32-or HCO3-  present
II	To the first portion from a(I) above  add dilute NaOH in drops then excess	White precipitate, soluble in excess	Pb2+, Al3+, Zn2+  likely present
III	To the second portion a(I) from above, add aqueous ammonia	White gelatinous precipitate, soluble in excess , gives a colourless solution	Zn2+ confirmed
B(I)	Y + distilled water, divide into four portions	Soluble, colourless solution	Transition ions absent, soluble ions like Na+, NH+, K+ likely present
II	To the first portion from b(I) above add dilute NaOH solution in drops then excess	White precipitate, soluble in excess	Zn2+, Pb2+ , Al3+ likely present
III	To the second portion from b(I) above add aqueous ammonia	White precipitate, insoluble in excess	Pb2+, Al3+ likely present
IV	To the third from b(I) above add dilute HCl or dilute BaCl2 solution	No visible reaction	Al3+ confirmed

 

Note:

·          All trioxocarbonate IV liberate carbon IV oxide when they react with dilute acid and they also liberate carbon IV oxide when they are heated strongly.

·         Lead ions, aluminium ions and Zinc ions show similar reactions with dilute

Sodium hydroxide solution.

·         Among the three ions, Zinc is the only soluble in excess of aqueous ammonia.

·         Lead ions give a white precipitate with dilute hydrochloric acid or any chloride while aluminium ions do not. To watch the Youtube video click here, you can watch part 2.