INTRODUCTION TO QUALITATIVE ANALYSIS

• Introduction to Qualitative Analysis

Test for carbons using H2S, NaOH and NH4OH, Confirmatory Test for the cat ions.

Introduction to Qualitative Analysis

Qualitative analysis involves examination of colour, flame test, effect of heat and confirmatory test for cat ion and anions.

Cations are metallic ions e,g Ca²⁺, Pb²⁺, Al³⁺, Cu²⁺, Fe²⁺ , Fe³⁺, etc

Rules in Qualitative Analysis

1. Your test solution should not be diluted too much
2. Use only small quantity of reagents

Examination of colour and physical state of specimen

            Substance              colour          physical state

1.          Sulphur                  yellow            solid

2.         Copper(ii)oxide       black             solid

3.         Iodine                   dark brown       solid

4.         Nitrogen iv oxide   reddish brown   gas

5.         Mercury                  white           liquid

Flame test

1. Deep green colour of flame indicate the presence of copper
2. Deep yellow colour indicate the presence of sodium
3. Brick red indicate calcium.

EVALUATION

1. State ten (10) examples of cations
2. Give the colour of the following substance.
3. Distilled water
4. Iron filling
5. Manganese(iv) oxide
6. Benzoic acid.

Test for Cations

The Cations are Ca²⁺, Zn²⁺, Al³⁺, Pb²⁺, Fe²⁺. Fe³⁺, Cu²⁺, NH4 ⁺

GENERAL EVALUATION

1. Give the common reagents used for confirmatory test for cations.
2. State the colour of the solution when the sample that contains the following dissolve in water:

a. Fe ²⁺             b. Cu ²⁺             c. Fe ³⁺

WEEKEND ASSIGNMENT

1. The following  give white gelatinous precipitate in NaOH except? (a) Al ₃₊ (b) pb₂₊ (c) CU ₂₊

(d) Zn₂₊

• One of the following gives ‘pop’ sound when contact with lighted splint. (a) O₂ (b) H₂ (c ) NH₃

(d) CO₂

• Example of cations that gives gas during its confirmatory test is (a) SO₃^2- (b) SO₄^2-  (c) CO₃^2-

(d) NH₄⁺

• Deep green colour of flame indicate the presence of (a) sodium (b) calcium    (c) copper (d) iron
• The only alkaline gas that changes moist red litmus paper to blue is (a)NH₃    (b) HCl (c) NaOH (d) NH₄OH

THEORY

1. Explain the confirmatory test for the following cations
2. State the flame test for the following :

a. Calcium         b. Copper          c. sodium            d. iron

READING ASSIGNMENT

School Chemstry by O.Y Ababio pages 165 – 183

Practical chemistry by R. I. Makanjuola pages 31-36.

Practical Chemistry for Schools and Colleges by Godwin O. Ojokuku pages 30 – 98.