OXIDES OF CARBON at a glance

 

CARBON (IV) OXIDE

Carbon (iv) oxide occurs in the  atmosphere, about 0.03%.

  Laboratory preparation

Carbon (iv) oxide is prepared in the laboratory by the action of dilute hydrochloric acid on calcium trioxocarbonate (iv) (marble chips or limestone).

 

CaCO_3(s)  +  2HCl_(aq) →CaCl_2(aq) + H₂O_(l) + CO_2(g)

2. It is also prepared by heating metallic trioxocarbonates (iv) (except those of Na and K), or the hydrogen trioxocarbonate (iv) of Na or K.

CuCO_3(s) → CuO_(s) +  CO_2(g)

 Dry CO2 is obtained by  passing the gas  through potassium hydrogen trioxocarbonate (IV) solution (to  remove any acid fumes, and then through fused Calcium chloride in a U-tube to remove the water vapour.)

The dry gas is then collected by downward delivery as it is heavier than air.

 The reaction  can also be prepared in Kipp’s apparatus

INDUSTRIAL PREPARATION

CO₂ is prepared industrially as a by product of fermentation or when limestone is heated strongly make quicklime.

 

PHYSICAL PROPERTIES

i.   CO₂ is a colourless gas 

ii.  It is an  odourless gas with a sharp refreshing taste.

iii.  It is about 1.5 times denser than air.

iv.  It is soluble in water.

v.   It turns damp blue litmus paper pink.

vi.  It solidifies on cooling (-78⁰C) to form a white solid known as dry ice.

 

CHEMICAL PROPERTIES

1. Reaction with water: Carbon (iv) oxide dissolves in water to form trioxocarbonate (iv) acid (Soda water), a weak, dibasic acid which ionizes slightly.

(a)  CO_2(g) + H₂O_(l) →H₂CO_3(aq) 

2. Reaction with alkalis: It reacts with alkalis to yield trioxocarbonate (iv) salts.

      CO_2(g) + 2NaOH_(aq) →Na₂CO_3(aq) + H₂O_(l)

Limited

with excess CO₂ reacts with alkalis to produce Hydrogen trioxocarbonate (iv) salt.

    CO_2(g)+ NaOH_(aq)→NaHCO_3(aq)

 

4.  When passed over  red hot coke. CO₂ is reduced to CO.

          CO_2(g)+ C_(s)→2CO_(g)

 

Test for CO₂: 

When CO2 is bubbled through  lime water (Calcium hydroxide), it will turn lime water turn milky. ( because of the formation of insoluble calcium trioxocarbonate)

     Ca(OH)_2(aq)+ CO_2(g) →CaCO_3(s)+ H₂O_(l).

If the gas is bubbled in excess, the milkiness disappears and turns to a clear solution due to the formation of soluble calcium hydrogen trioxocarbonate (iv).

CaCO_3(s) + H₂O_(l) +CO_2(g) →Ca(HCO₃)_(aq)

 

Uses of carbon (IV) oxide

i.     It is used in making  carbonated (aerated) drinks. It is responsible their refreshing taste. 

 ii.   It is used in fire extinguishers because it does not support combustion.

iii..  It is used in the Solvay Process for the manufacture of Na₂CO₃ (washing soda)  

iv..    It is used as a leavening agent in the baking of bread. 

v.      Solid CO₂ (i.e dry ice) is used as a refrigerant for perishable goods e.g ice cream.

vi.     Gaseous CO₂ is used to preserve fruits.

vii.    CO₂ is also used as a coolant in nuclear reactors.

CARBON (II) OXIDE

LABORATORY PREPARATION

Carbon (II) oxide is prepared by the dehydration of methanoic (formic) acid or ethanedioic (oxalic) acid, using concentrated tetraoxosulphate (vi) acid.

HCOOH_(l)^{Conc. H2SO4}→CO_(g) + H₂O
Methanoic acid

  COOH
   |        ^{Conc. H2SO4}→  CO2 + CO
  COOH
ethanedioic 

 The CO2 is removed by passing the gaseous mixture through concentrated NaOH 

                                                                                                 

Physical Properties Of Carbon (ii) Oxide

i. Carbon (ii) oxide is a colourless, odourless and tastless

ii. It is a poisonous gas

(2) It is insoluble in water, but dissolves in a solution of ammoniacal copper (i) chloride.

(3) It is neither lighter nor heavier than air.

(4) It is neutral to litmus.

Chemical Properties of Carbon (ii) oxide

(1) As a reducing agent:-Most metallic oxides are reduced to the metals on reaction with CO  oxidizing it to CO₂.

CuO_(s) + CO_(g) →Cu_(s)+ CO_2(g)

Fe₂O_3(s) + 3CO_(g) →2Fe_(s) + 3CO_2(g

2.  Combination reaction

i.  With oxygen: CO burns in air with a faint pale blue flame to form CO₂ .

       2CO_(g)+ O_2(g) →2CO_2(g)

ii.  With haemoglobin: CO has equal affinity for the red blood cells as oxygen, and when exposed to as little as 0.005% of the gas  it combines irreversibly with haemoglobin in the red blood cells to form carboxy-haemoglobin. These prevents oxygen from reaching the blood and this can cause death by suffocation.

 

Test for Carbon (ii) oxide

Inserted a lighted splinter into a test tube containing the unknown gas, if it burns with a pale blue flame and turns and some lime water after burning, the the gas is carbon (ii) oxide 

 

Uses of Carbon (ii) oxide

(1) CO is used for extraction of metals from their ores.

(2) It is an important constituent of gaseous fuels like producer gas and water gas.

(3) CO gas is used in the manufacture of organic compounds like methyl alcohol, synthetic petrol. 

 

OBJECTIVE QUESTIONS 

Oxides of Carbon – 15 Objective Questions

1. Which of the following is known as the most common oxide of carbon?
   A. Carbon(IV) oxide
   B. Carbon(II) oxide
   C. Sulphur dioxide
   D. Nitrogen dioxide

2. The chemical formula of carbon (II) oxide is:
   A. CO₂
   B. C₂O
   C. CO
   D. C₂O₃

3. Carbon (II) oxide is mainly produced by:
   A. Complete combustion of carbon
   B. Incomplete combustion of carbon
   C. Reaction of acids with metals
   D. Electrolysis of water

4. Which oxide of carbon turns limewater milky?
   A. Carbon monoxide
   B. Carbon dioxide
   C. Carbon soot
   D. Carbon black

5. Carbon monoxide is dangerous because it:
   A. Has a bad smell
   B. Causes skin burns
   C. Combines with haemoglobin in blood
   D. Explodes in air immediately

6. Which of the following properties belongs to carbon dioxide?
   A. It is poisonous
   B. It supports burning
   C. It is acidic in nature
   D. It is lighter than air

7. The gas used in fire extinguishers is:
   A. Oxygen
   B. Hydrogen
   C. Carbon (IV) oxide
   D. Nitrogen

8. Which oxide of carbon is neutral in nature?
   A. Carbon dioxide
   B. Carbon monoxide
   C. Carbonic acid
   D. Charcoal

9. Carbon dioxide can be prepared in the laboratory by reacting:
   A. Sodium chloride with water
   B. Calcium carbonate with dilute acid
   C. Zinc with sodium hydroxide
   D. Copper with water

10. The relative molecular mass of carbon (IV)oxide is:
    A. 28
    B. 16
    C. 32
    D. 44

11. Which of the following statements about carbon monoxide is correct?
    A. It has a pungent smell
    B. It is colourless and poisonous
    C. It turns blue litmus red
    D. It supports respiration

12. Dry ice is the solid form of:
    A. Carbon monoxide
    B. Carbon soot
    C. Carbon dioxide
    D. Carbonic acid

13. Which process removes carbon dioxide from the atmosphere naturally?
    A. Respiration
    B. Combustion
    C. Photosynthesis
    D. Fermentation

14. Excess carbon dioxide in the atmosphere contributes to:
    A. Acid rain only
    B. Ozone depletion only
    C. Greenhouse effect
    D. Nuclear radiation

15. When carbon dioxide is passed through limewater for a long time, the milkiness disappears because:
    A. Oxygen is formed
    B. Calcium carbonate decomposes
    C. Soluble calcium hydrogen carbonate is formed
    D. Water evaporates
16.  Kipp’s apparatus is important in the laboratory because it

         A. allows intermittent supply of gases. 

         B. is used for preparing poisonous gases. 

         C. is used to prepare light gas. 

         D. is used to prepare sensitive gas

     17.  Gas prepared by the reaction between methanoic acid and concentrated tetraoxosulphate (vi) acid is 

         A. SO₂           

          B.  CO             

          C. CO₂           

          D. H₂S.

    18. Gas which dissolves in ammoniacal copper (i) chloride but insoluble in water is

        A. NH₃ 

         B. CO 

        C. N₂O 

        D.  CO₂.

   19. Where else is CO₂ found in free state apart from the atmosphere?

       A. In carbonated drinks. 

       B. Dissolved form in water. 

       C.  In corals. 

       D. In limestone region

    20. It is dangerous to stay in a badly ventilated room which has a charcoal fire because of the presence of 

     A. carbon (ii) oxide 

     B.carbon (iv) oxide 

     C. hydrogen sulphide 

     D.  producer gas.

THEORY QUESTIONS 

1(a)i  Describe the laboratory preparation of dry Carbon (iv) oxide.

   ii. write the equation for the preparation of CO2

   iii. mention two properties of CO2

1b. State what is observed when 

(i) excess CO₂ is bubbled through lime water. 

(ii) the solution in b(i) above is heated.

2(a)i. What  property of CO₂ makes it to be used in 

(I) carbonated drinks (II ) fire extinguishers

3(a)Draw  the laboratory preparation of carbon (ii) oxide done in a fume chamber?

2ii  Explain why Carbon (ii) oxide cannot be collected by any method of delivery

3.  Write two equations to show the chemical properties of Carbon (ii) oxide