Lesson Notes By Weeks and Term - Senior Secondary 3

Qualitative and quantitative analysis 2

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TERM - 2nd TERM

WEEK THREE

Class: Senior Secondary School 3

Age: 17 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Chemistry

Topic: Qualitative and quantitative analysis 2

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. identify ions in solution.
  2. Test for simple gases like NH3, NO3, Oxygen etc

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, relevant salts, acids, bases, starch etc.

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S

ACTIVITY

STEP 1

INTRODUCTION

The teacher guide students to identify ions in solution.

 

Students pay

attention

STEP 2

EXPLANATION

Teacher guide students to test for Test for hydrogen NH3, HCl, NO3, Oxygen, CO2, Cl

Students pay

attention and

participate

STEP 3

NOTE TAKING

The teacher writes a summarized

note on the board

 

The students

copy the note in

their books

 

NOTE

QUANTITATIVE AND QUALITATIVE ANALYSIS 2

Identification of Ions

In qualitative analysis, we identify, the elements and compounds that are present in a sample of a given substance.

The preliminary test we carried out under the following headings:

  1. Appearance of the compound (colour)
  2. Flame test
  3. Action of heat(identification of gases)

Appearance

Appearance

Probable salt/compound

Green

Iron II salts, Iron II salts are usually pale green

Yellow/brown

Lead(II) oxide, Iron(III) salt solution, canduim sulphide - yellow

Black or red

CuO, PbS, CuS, Ag2S, HgS

White colourless

Ca²+, Pb²+, NH⁴+, Na+, AI³+, Zn²+, salts and ZnS, MnS

Smell of ammonia

Ammonium salt

Smell of Sulphur

Trioxosulphate(IV) salts

Smell of hydrogen sulfide

Sulphides

 

Flame test

Colour from flame test

Probable ion

Brick red

Ca²+

Deep green

Cu²+

Blue

Pb²+

Persistent golden yellow

Na+

Persistent lilac

K+

Persistent light green

Ba²+

 

Action of heat on specimen

Observation

Inference

White when cold and yellow when hot

Zn²+(ZnO) present

Yellow when cold  and reddish brown when hot

Pb²+(PbO)

Reddish brown

Fe³+(Fe2O3)

Water vapor when condenses at the upper part of the tube

Hydrated salts HCO3- or OH- present

White sublimate

Ammonium salt

 

Gases evolved on heating

Gas

Inference

NO2

NO3- present

CO2

CO²-3 or HCO3- present

O2

NO3- present

SO2

SO²-3 present

NH3

NH+4 present

 

TEST FOR GASES

Gas

Colour/smell

Test

Result if positive

Cl2

Greenish yellow, pungent

(a) Moist blue litmus paper

Turns red then bleaches it (acidic)

Bromine is liberated and solution turns yellow or orange.

NO2

Reddish brown, pungent

(a) moist blue litmus paper

(b) Bubble through fresh FeSO4 solution

Turns red(acidic)

Solution turns blue

NH3

Colourless pungent

Smell like that of urine

(a) moist red litmus paper

(b) bring in contact with drop of conc. HCl on a glass rod

Turns blue (alkaline gas)

White dense fumes due to the presence of NH4Cl

HCl(g)

Colourless

(a) damp blue litmus paper

(b) blow across mouth of the test tube

(c) bring in contact with drop ammonia solution on a glass rod.

Turns red(acidic)

Copious fuming

White dense fumes of ammonium chloride

CO2

Colourless

Odorless

(a) damp blue litmus paper

(b) bubble through the lime water in excess of it

Turns red (acidic)

Turns milky (ppt of CaCO3) milky color disappears due to formation of CaHCO3

O2

Colourless

Odourless

(a) damp blue and red litmus paper

(b) glowing splint

No change (neutral)

Ignites or rekindles glowing splint

H2

Colourless

Odourless

(a) damp blue or red litmus paper

(b) lighted splint

No effect (neutral gas)

Little explosion occurs giving pop sound; burns with blue flame, if mixed with air

H2O (g)

Colourless

Odourless

(a) damp blue or red litmus paper

(b) Anhydrous CuSO4 (white in colour)

No change ( neutral gas)

It turns to blue crystal of CuSO4 5H2O

 

EVALUATION: Sample D, E, F and G are solutions of CuSO4, NH4Cl, FeCl3 and Zn(NO3)2, but not necessarily in that order. Using NaOH(aq) and litmus paper with gentle heating where necessary, state in a tabular form how you would identification D, E, F and G.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively