Lesson Notes By Weeks and Term - Senior Secondary 1

Carbon and its compounds III

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  4. Carbon and its compounds III

Term: 3rd Term

Week: 4

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:       

Subject:      Chemistry

Topic:-       Carbon and its compounds III

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

  1. Explain the oxides of carbon
  2. Discuss carbonates

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 Coal and coke

Students pay attention

STEP 2

EXPLANATION

He explains oxides of  carbon; their properties, preparation and uses

 

Students pay attention and participates

STEP 3

DEMONSTRATION

He discusses carbonates; their properties, preparation and uses

 

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

CARBON AND ITS COMPOUNDS

OXIDES OF CARBON

Carbon forms two kinds of oxides, carbon (IV) oxide, CO2, and carbon (II)

oxide, CO.

Both oxides are obtainable as the products of combustion of carbon.

 

Carbon (IV) Oxide

Preparation:

  1. Carbon (IV) oxide is made in the laboratory through the action of dilute hydrochloric acid or trioxonitrate (V) acid on metallic trioxocarbonate (IV) or hydrogen trioxocarbonate.

CaCO3 + 2HCl → CaCl2 + H2O + CO2

CaCO3 + 2HNO3 → Ca (NO3) + H2O + CO2

NaHCO3 + HCl → NaCl + H2O + CO2

A Kipp’s apparatus is used to provide intermittent supply of the gas whenever it is needed in the laboratory

 

  1. Action of heat on metallic trioxocarbonate (IV) apart from those of sodium and potassium or the hydrogen trioxocarbonates (IV) of sodium and potassium

CaCO3 → CaO + CO2

2NaHCO3 → Na2CO3 + H2O + 2CO2

Carbon (IV) oxide is acquired industrially as by-product in the fermentation process and manufacture of quicklime (CaO) from limestone (CaCO3).

 

Physical properties:

  1. CO2 is a colourless, odourless and tasteless gas.
  2. It is around 1.5 times denser than air.
  3. This is moderately soluble in water.
  4. It turns damp blue litmus paper red as CO2 dissolves in water to form an acidic oxide, trioxocarbonate (IV) acid.
  5. This can readily be liquefied and solidified (- 78°C). Solid CO2 is termed as cardice or dry-ice.

 

Chemical properties:

  1. CO2 doesn't burn nor does it support the combustion. Though burning magnesium decomposes CO2 leaving a black carbon deposit and magnesium (II) oxide ash.

CO2 + 2Mg → 2MgO + C

 

  1. CO dissolves in the water to form trioxocarbonate (IV) acid (that is, soda water). This is a weak acid.

CO2 + H2O ⇋ H2CO3

 

  1. CO2 reacts directly by alkalis example: NaOH, to form trioxocarbonates (IV).

NaOH + CO2 + H2O → 2NaHCO3

 

Test for CO2

Whenever CO2 is passed via the alkali, calcium hydroxide (that is, limewater), the lime water turns milky due to the precipitation of insoluble calcium trioxocarbonate (IV). This reaction is employed to test for CO2.

Ca(OH)2    + CO2 →   CaCO3 + H2O

Limewater Insoluble

 

Though, whenever excess gas is bubbled, the milkiness disappears leaving a clear solution as the Soluble trioxocarbonate (IV) is transformed to soluble hydrogen trioxocarbonate (IV). (This is used as a test for carbon dioxide)

CaCO3 + H2O + CO2 → Ca(HCO3)2

 

Uses

  1. Most of the fire extinguishers make use of carbon (IV) oxide to put out fires as the gas doesn't support combustion.
  2. Carbon (IV) oxide is employed in the manufacture of trioxocarbonates.
  3. Yeast and baking powder are employed in baking to produce carbon (IV) oxide that causes the dough to rise, making dough light.
  4. Solid carbon (IV) oxide that is, dry ice is employed as a refrigerant for perishable goods, and as a coolant in the nuclear reactors.
  5. Carbon (IV) oxide is employed to give carbonated (or aerated) drinks a pleasant and refreshing taste.
  6. Green plants make use of CO2 throughout photosynthesis.

 

Carbon (II) Oxide:

CO is made by the incomplete combustion of carbon compounds, like octane, C8H18, found in petrol.

2C8H18 (l) + 17O2 (g) → 16 CO (g) + 18 H2O (l)

 

Preparation:

  1. Carbon (II) oxide is made by passing carbon (IV) oxide over red-hot carbon

CO2+C→2CO

This can as well be made by dehydrating methanoic acid, HCOOH, or ethanedioic acid, C2H2O4, by utilizing concentrated tetraoxosulphate (VI) acid, that act as the dehydrating agent.

 

  1. The preparation of CO should be done in the fume cupboard as the gas is poisonous. In the later reaction, the CO2 is eliminated by passing gaseous products via concentrated sodium hydroxide.

 

Physical Properties:

  1. Carbon (II) oxide is a colourless, tasteless and odourless gas.
  2. It is insoluble in water, however dissolves in a solution of ammoniacal copper (I) chloride.
  3. It is to some extent less dense than air.
  4. It consists of no effect on litmus

 

Chemical Properties:

  1. Act as a reducing agent:

PbO (s) + CO (g) → Pb(s) + CO2(g)

H2O(g) + CO(g) H2(g) + CO2(g)

  1. It burns in air having a blue flame to provide carbon (IV) oxide

2C0 + O2 → 2CO2

  1. The poisoning nature of Carbon (II) oxide is as a result of its reaction having haemoglobin in the red blood cells and therefore prevents the haemoglobin from transporting oxygen in our body. Death resultant from CO poisoning take place whenever the supply of oxygen to the body becomes not enough as the carrier haemoglobin is not available for this function.

 

Uses

  1. CO is utilized as a reducing agent in the extraction of metals example: iron from its ores.
  2. CO is the significant constituent of gaseous fuels such as producer gas (CO + N2) and water gas (CO + H2).

 

Trioxocarbonate (IV) and Hydrogen Trioxocarbonate (IV)

Trioxocarbonates (IV) and hydrogen trioxocarbonates (IV) are the inorganic compounds of carbon. Trioxocarbonates (IV) acid reacts with some free metals, metallic oxides and alkalis to form trioxocarbonate (IV) salts.

Zn + H2CO3 → ZnCO3 + H2

Trioxocarbonate (IV) salts are of two kinds:

  1. Normal trioxocarbonate (IV) MCO3 and
  2. Acidic hydrogen trioxocarbonate (IV) MHCO3

 

Preparation of soluble trioxocarbonate (IV) salt:

The water soluble trioxocarbonate (IV) salts are sodium, potassium and ammonium trioxocarbonate (IV). They are generally made by passing carbon (IV) oxide via a solution of corresponding alkali.

2NaOH + CO2 → Na2CO3 + H2O

 

Preparation of insoluble trioxocarbonate (IV) salts:

Most of the metallic trioxocarbonate (IV) are insoluble in water. The common methods for preparing them are:

  1. Reaction of a base, metals or metallic oxide with trioxocarbonate (IV) acid

Ca(OH)2 + H2CO3 → CaCO3 + 2H2O

Zn + H2CO3 → ZnCO3 + H2

MgO + H2CO3 → MgCO3 + H2O

 

  1. By adding a solution of sodium trioxocarbonate (IV) to a solution of the corresponding metal salt.

Na2CO3 + CaCl2 → CaCO3 + 2NaCl

Na2CO3 + 2AgNO3 → 2NaNO3 + Ag2CO3

 

Hydrogen Trioxocarbonate (IV) salts:

These are the acid salts of trioxocarbonate (IV) acid made whenever a metal or ammonium radical substitutes one of the two hydrogen atoms in the molecule. They are soluble in water.

Hydrogen trioxocarbonates (IV) might be prepared through passing CO2 via a solution of the corresponding hydroxides or trioxocarbonates (IV).

NaOH + CO2 → NaHCO3

Na2CO3 + CO2 + H2O → 2NaHCO3

 

Properties of trioxocarbonates (IV) salts:

  1. All trioxocarbonate (IV) salts apart from those of sodium, potassium and barium, decompose on heating to release carbon (IV) oxide.

 

ZnCO3 → ZnO + CO2

(NH4)2CO3 → 2NH3 + CO2 + H2O

The entire hydrogen trioxocarbonates (IV) as well decompose on heating the solid or solution to provide carbon (IV) oxide, water and the corresponding trioxocarbonates (IV).

2KHCO3 → K2CO3 + H2O + CO2

 

  1. All the trioxocarbonate (IV) and hydrogen trioxocarbonate (IV) salts react by dilute acids to form carbon (IV) oxide water and a salt.

CaCO3 + 2HCl → CaCl2 + H2O + CO2 Ca(HCO3)2 + 2HCl → CaCl2 + 2H2O + 2CO2

       3. All trioxocarbonate are insoluble except that of sodium, potassium and ammonium. While all hydrogen trioxocarbonates are soluble

 

Uses of some significant trioxocarbonate (IV) salts:

  1. Na2CO3 is utilized in the manufacture of glass, soap and detergents, and also in the production of paper and pulp.
  2. NaHCO3 is employed in baking powder to discharge CO2 gas that helps the dough to rise throughout baking. It is as well employed as medicine to relieve indigestion example: in Andrews liver salts. This is utilized in dry-powder fire extinguishers.
  3. CaCO3 is utilized in the production of cement, chalk and significant industrial chemicals example: CaO and NH3.

 

EVALUATION:    1. Explain the oxides of carbon: their preparation, uses physical and chemical properties

  1. Discuss Carbonates; their preparation, properties and uses

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively