CARBON
(IV) OXIDE
Carbon (iv)
oxide occurs in the atmospheric. 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).
CaCO3(s) + 2HCl(aq) →CaCl2(aq) +
H2O(l) + CO2(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.
CuCO3(s) → CuO(s) +
CO2(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) CO2(g) + H2O(l) →H2CO3(aq)
2. Reaction
with alkalis: It reacts with alkalis to yield trioxocarbonate (iv) salts.
CO2(g) + 2NaOH(aq) →Na2CO3(aq) +
H2O(l)
Limited
with excess
CO2 reacts with alkalis to produce Hydrogen trioxocarbonate
(iv) salt.
CO2(g)+ NaOH(aq)→NaHCO3(aq)
4.
When passed over red hot coke. CO2 is reduced to CO.
CO2(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)+ CO2(g) →CaCO3(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).
CaCO3(s) +
H2O(l) +CO2(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)+ CO2(g)
Fe2O3(s) +
3CO(g) →2Fe(s) +
3CO2(g
2.
Combination reaction
i.
With oxygen: CO burns in air with a faint pale blue flame to form CO2 .
2CO(g)+ O2(g) →2CO2(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
1. 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
2. Gas
prepared by the reaction between methanoic acid and concentrated
tetraoxosulphate (vi) acid is
(a) SO2
(b)
CO
(c) CO2
(d) H2S.
3. Gas which
dissolves in ammoniacal copper (i) chloride but insoluble in water is
(a) NH3
(b) CO
(c) N2O
(d) CO2.
4. 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
5. 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