CARBON & SILICON
OXIDES
Prepared by:ZHUMAN GAZIZA
 Carbon(II)
monoxide - a colorless,
poisonous gas is lighter than air (under
normal conditions), tasteless and
odorless. Chemical formula - CO.
Getting :
The industrial method:
The effect of temperature on the equilibrium reaction:
CO2+C→2CO
Formed during combustion of carbon or compounds
based on it (e.g., gasoline) in the conditions of lack of
oxygen:
2C+O2→2CO (thermal effect of this reaction 220 kJ),
Laboratory method:
The decomposition of liquid formic acid under the
action of hot concentrated sulfuric acid, or the
transmission of gaseous formic acid on phosphorus
oxide P2O5
HCOOH→H2O+CO
You can also handle formic acid chlorosulfonic. This
reaction is already at ordinary temperature.
HCOOH+ClSO3H→H2SO4+HCl+CO
Recovery from carbonate zinc magnesium when
heated:
Mg+ZnCO3→MgO+ZnO+CO
Below 830 ° C is a strong reducing CO, - higher - hydrogen.
Therefore, the reaction equilibrium
H2O+CO2→CO2+H2
Carbon monoxide (II) blue flame burns [1] (the reaction
initiation temperature of 700 ° C) in air:
2CO+O2→2CO2 (ΔG ° = -257 kJ 298, ΔS ° 298 = -86 J / K).
Carbon monoxide (II) is reacted with halogens. The greatest
practical use to get a reaction with chlorine:
CO+Cl2→COCl2
Carbon monoxide (II) is reacted with the chalcogen.
With sulfur forms a carbonyl sulphide COS, the
reaction proceeds under heating, according to the
equation:
CO+S →COS(ΔG ° = -229 kJ 298, ΔS ° 298 = -134 J
/ K).
Restores SO2:
2CO+SO2→2CO2+S
C transition metals forming flammable and toxic
compounds - CARBONYLS, such as Cr(CO)6, Ni(CO)4,
Mn2CO10, Co2(CO)9, etc. Some of them are volatile.
n CO+Me→Me(CO)n
Carbon oxide(II) slightly soluble in water, but does not react
with it. It also does not react with alkaline solutions and acids.
However, reacts with molten alkali with the formation of the
corresponding formate:
CO+KOH→HCOOK
Interesting reaction of carbon oxide(II) with metallic potassium
in ammonia solution. This forms an explosive compound
discoverwhat potassium:
2K+2CO→K2C2O2
Reaction with ammonia at high temperatures can be
important for industry connection - cyanide HCN.
The reaction proceeds in the presence of a catalyst
(thorium dioxide ThO2) by the equation:
CO+NH3→H2O+HCN
The most important property of carbon oxide(II) is
its ability to react with hydrogen with the formation
of organic compounds (the process of Fischer Tropsch synthesis)
CO + y H2 →alcohols + linear alkanes.
This process is a source of production of major
industrial products such as methanol, synthetic diesel
fuel, polyhydric alcohols, oils and greases.
Carbon(IV) dioxide is a colorless gas (under normal
conditions), without odor, with a slightly sour taste.
Density at normal conditions 1.97 kg/m3. At
atmospheric pressure, carbon dioxide does not exist
in the liquid state, passing directly from the solid to
the gaseous state. Solid carbon dioxide is called dry
ice. At high pressure and normal temperatures, the
carbon dioxide passes into the liquid that is used for
storage.
Getting:
Get carbon dioxide thermal decomposition of salts of
carbonic acid (carbonates), for example, calcination of
limestone:
CaCO3 = CaO + CO2
or by the action of strong acids on carbonates and
bicarbonates:
CaCO3 + 2HCl = CaCl2 + H2O + CO2
NaHCO3 + HCl = NaCl + H2O + CO2.
Chemical properties:
Chemical properties of carbon dioxide refers to acidic oxides.
When dissolved in water forms carbonic acid. Reacts with
alkalis with the formation of carbonates and bicarbonates.
Reacts electrophilic substitution (e.g., phenol) and nucleophilic
attachment (for example, magnetogenesis connections).
Carbon oxide(IV) does not support combustion. It only burn
some active metals.
2Mg+CO2→2MgO+C
The interaction with the oxide of the active metal:
CaO+CO2→CaCO3
When dissolved in water forms carbonic acid:
CO2+H2O→H2CO3
Reacts with alkalis with the formation of carbonates and
bicarbonates:
Ca(OH)2+CO2→CaCO3+H2O(qualitative reaction for
carbon dioxide)
KOH+CO2→KHCO3
The silicon oxide(II) (silicon monoxide) SiO - retinoid
amorphous substance, under normal conditions, is resistant
to the action of oxygen. Refers to not salt-forming oxides.
The silicon monoxide is an unstable connection, air is
slowly oxidized to SiO2. This refractory dark brown
powder, has good dielectric properties and mechanical
strength.
Solid silicon monoxide is not soluble in acids, except
hydrofluoric acid, easily soluble in alkalis and release of
hydrogen, is a good reducing agent.
Getting:
The silicon monoxide can be obtained by heating the
silicon in the lack of oxygen at temperatures above
400 °C:
2Si+O2→2SiO
Also SiO is formed when restoring SiO2 silicon at
high temperatures (for example, on the surface of the
crucible in the production of monocrystalline silicon
by the Czochralski method):
SiO2+Si→2SiO
The silicon oxide (IV)
Silicon dioxide is widely distributed in nature. Crystalline silica is
quartz, rock crystal, chalcedony, Jasper, the basis of quartz sand. Very
solid, durable, refractory substance. At normal pressure and
temperature there are three crystalline modifications of SiO2:
quartz, tridymite and cristobalite. For each modification of the
known low-temperature α - and high-temperature β-form. They are
all built from SiO4 tetrahedra connected with other tetrahedra all
four oxygen atoms in a three-dimensional lattice.
Mutual arrangement of the tetrahedra in various modifications
completely different, but between the α - and β - forms differ
slightly, so between transformations occur at low temperatures, and
mutual transitions between different modifications require breaking
bonds Si - O - Si, so they run at high temperatures and slow.
Getting:
Synthetic silica obtained by heating the silicon to a
temperature of 400-500 °C in an atmosphere of oxygen, and
the silicon dioxide is oxidized to SiO2. As well as thermal
oxidation at high temperatures.
In the laboratory of synthetic silicon dioxide can be obtained
by the action of acids, even a weak acetic acid, soluble silicates.
For example:
Na2SiO3+2CH3COOH→2CH3COONa+H2SiO3
silicic acid immediately breaks down into water and SiO2
precipitated.
Natural silicon dioxide in the form of sand is used where you
don't need high purity material.
Chemical properties:
Chemical properties of various modifications similar to each
other.
Interaction with metals
At temperatures above 1000 °C reacts with active metals,
thereby forming silicon:
SiO2 + 2Mg = Si + 2MgO
or when excess reductant - silicides:
SiO2 + 4Mg =Mg2Si + 2MgO.
Interaction with nonmetals
Reacts with hydrogen:
SiO2 + N = Si + NO.
Interacts with carbon:
SiO2 + 3C = SiС + 2SD.
Properties of acid oxide
Silicon dioxide is a typical acidic oxide, but is not soluble in
water, in the event of fusion reacts with alkalis:
SiO2 + 2KOH =K2SiO3+ H2O,
major oxides:
SiO2 + MgO = MgSiO3
and carbonates of alkali metals:
SiO2 + K2CO3= K2SiO3 + CO2.
With acids do not react with the exception of hydrofluoric
acid:
SiO2+ 6HF = H2SiO6+ 2H2O