Lesson Notes By Weeks and Term - Senior Secondary 1

Term: 2^nd Term

Week: 10

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:       

Subject:      Chemistry

Topic:-       Acids, Bases and Salts II

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

1. Define neutralization
2. Discuss the various common oxides
3. Discuss how to prepare soluble and insoluble salts

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION	TEACHER’S ACTIVITY	STUDENT’S ACTIVITY
STEP 1 INTRODUCTION	The teacher reviews the previous lesson on acids, bases and salts	Students pay attention
STEP 2 EXPLANATION	He defines neutralization. He discusses the various oxides	Students pay attention and participates
STEP 3 DEMONSTRATION	He discusses how to prepare soluble and insoluble salts	Students pay attention and participate
STEP 4 NOTE TAKING	The teacher writes a summarized note on the board	The students copy the note in their books

 

NOTE

ACIDS, BASES AND SALTS

NEUTRALIZATION

It is the reaction between acid and base to form salt and water only. From ionic equation, we know that the reaction only involves H⁺ ions from acids with OH^-ions from alkali to form water.

E.g. NaOH + H₂SO₄

 

H2SO4(aq) + NaOH(aq)       Na2SO4(aq) + H2O(g)

Ionic equation is:

H⁺_(aq) + OH^-_(aq)→H₂O_(g)

 

E.g Plants don’t grow well in acidic soil. Quicklime (calcium hydroxide) is added to

 

Neutralize the acidity of soil according to equation

Acid _(aq) + Ca(OH)_2(aq)   Ca(acid anion)_(aq) + H₂O_(g)

 

Reaction between Base and Ammonium Salts E.g. Reaction between NaOH and NH₄OH

NaOH_(aq) + NH₄Cl_(aq)    Na_(aq) + NH_3(g) + H₂O(g)

Ionic equation:

NH₄⁺_(aq) + OH^-_(aq) NH_3(g) + H₂O_(g)

 

Acidic Oxide, Basic Oxide, Amphoteric Oxide, Neutral Oxide

1. Acidic Oxides are oxide of non-metals, usually gases which reactswith water to produce acids, CO₂, NO₃, P₄O₁₀, SO₂
2. Basic Oxides are oxides of metals, usually solid which reacts with water to produce alkalis, e.g. CaO, K₂O, BaO
3. Amphoteric Oxides are oxides of transition metals, usually solid, which reacts with acids/alkalis to form salt and water, e.g. Al₂O₃, FeO, PbO
4. Neutral Oxides are oxides that do not react with either acids or alkalis, hence do not form salts, e.g. H₂O, CO, NO

 

Preparation of Salts; Soluble and Insoluble Salts

Soluble

All Trioxonitrate (V) are soluble

All Tetraoxosulphate (VI) are soluble except BaSO₄, CaSO₄, PbSO₄ All Chlorides are soluble except PbCl₂ and AgCl

Potassium, Sodium, Ammonium salts are generally soluble -

All Trioxocarbonate (IV) are insoluble except K₂CO₃, Na₂CO₃,

NH₄CO₃ which are soluble

All metallic oxides insoluble except K₂O and Na₂O

 

Preparation of Insoluble Salts

Insoluble salts,

e.g. BaSO₄, CaSO₄, PbSO₄, PbCl₂, AgCl

Most trioxocarbonate (IV), can be prepared by reacting compound containing the wanted cation with another compound containing

 

the wanted anion. This is precipitation reaction. E.g. Preparation of BaSO_4.

First BaCl₂, since it contains wanted barium ion, is reacted with K₂SO₄, since it contains wanted Tetraoxosulphate (VI) ion, to produce solid BaSO₄ & aqueous KCl. BaSO₄ then separated from KCl by filtration, leaving filtrate of KCl and BaSO₄ left on filter paper. Salt is washed with water to completely remove KCl & filter paper is squeezed with another filter paper to dry BaSO₄.

 

 

Preparation of Soluble Salts By Neutralization.

E.g. Reacting Zn with H₂SO₄.

 

Zn(s) + H2SO4 (aq)

 

To prepare ZnSO₄

ZnSO4 _(aq)

Zn is added to H₂SO₄until in excess to ensure no more H₂SO₄ is present. Then the mixture is filtered off to separate Zn from ZnSO₄. The filtrate (ZnSO₄) is then placed in evaporating dish to evaporate most of water then it’s cooled after ZnSO₄ crystals are formed. The crystals then filtered and squeezed between filter papers to dry.

 

By Reacting Insoluble Base with Acid E.g. Reacting MgO with Acids

MgO(s) + H2SO4(aq)àMgSO4(aq) + H2O(l)

 

By Reacting trioxocarbonate (IV) with Acid E.g. Reacting K₂CO₃ with Acids

K2CO3(s) + H2SO4(aq)àK2SO4(aq) + CO2 (g) + H2O(l)

The same process is used as reaction of acid with metal, just that carbon (IV) oxide is produced. The gas produced can be tested by

 

bubbling it into lime water which will turn colourless limewater into milky colour.

EVALUATION:    1. Define neutralization

2. Discuss three common oxides
3. Outline steps in the preparation of soluble and                    insoluble salts

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively