(i) Carbon form large number of hydrides e.g. Alkanes, Alkenes.

(ii) Hydrides of `Si` are silanes with formula `Si_nH_(2n+ 2)`. These are also called as Silicon alkanes.

Eg. `SiH_4` Monosilicane Silicon methane

`Si_2H_6` Disilicane Silicon ethane

(iii) Silanes with 'n' up to `8` are known.

(iv) Hydrides of `Ge` are called Germains.

General Formula : `Ge_n H_(2n +2)`

(v) Tin has only two hydrides i.e.

(a) Stannane - `SnH_4`

(b) Distannane - `Sn_2H_6`

(vi) Lead has only one hydride i.e.

Plumbane - `PbH_4`

(vii) Thermal stability of hydrides `downarrow` because (`Delta`E.N. decreases).

Carbon reacts with oxygen to form three types of oxides-

(a) Carbon monoxide `CO`

(b) Carbon dioxide `CO_2`

(c) Carbon suboxide `C_3O_2`

(i) By incomplete combustion of carbon

`2C + O_2 rightarrow 2CO`

(ii) Reduction of oxides of heavy metals with carbon

`ZnO + C rightarrow Zn + CO`

`Fe_2O_3 + 3C rightarrow 2Fe + 3CO`

`PbO + C overset(Delta) rightarrow Pb + CO`

(iii) By dehydration of formic acid with conc.`(H_2SO_4)` (laboratory method) :

`undersettext(formic acid)(HCOOH)underset(373K)overset(H_2SO_4)rightarrow undersettext(pure)(CO+H_2O)`

(iv) By action of conc. `H_2SO_4` on potassium ferrocyanide

`undersettext(pot. ferrocyanide)(K_4[Fe(CN)_6]) + 6H_2SO_4 + 6H_2O overset(Delta) rightarrow 2K_2SO_4 + FeSO_4 + 3(NH_4)_2SO_4 + 6CO`

Physical Properties :

(i) It is a neutral oxide.

(ii) Colourless & odourless gas, slightly soluble in water.

(iii) Poisonous nature due to its ability to form a stable complex with the haemoglobin present in the red blood cells.

Haemoglobin `+ CO rightarrow` carboxy haemoglobin

Due to formation of stable complex with `CO`, Haemoglobin looses its `O_2` carrying capacity which causes death.

Chemical Properties :

(i) Formation of metal carbonyls

`Ni + 4CO overset(330-340K) rightarrow undersettext(Nickel carbonyl)[Ni(CO)_4]`

`Fe + 5CO underset(100atm)overset(473K) rightarrow undersettext(iron carbonyl)(Fe(CO)_5)`

(ii) Absorption : `CO` is readily absorbed by a soln. of `CuCl` in conc. `HCl` or `NH_3` due to the formation of soluble complexes

`CuCl + NH_3 + CO rightarrow undersettext(soluble complex)([Cu(CO)NH_3]^(+)Cl^(-)`

`CuCl + HCl + CO rightarrow undersettext(soluble complex)[H^(+)[Cu(CO)Cl_2]^(-)]`

(iii) With `Cl_2` :

`CO + Cl_2 undersettext(or camphor) oversettext(sunlight) -> undersettext[Phosgene (poisonous)](COCl_2)`

(iv) With `NaOH` :

`CO + NaOH undersettext(high T) oversettext(high p) rightarrow HCOONa`

(i) It reduces iodine pentoxide to iodine & this iodine can be titrated with standard sodium thiosulphate solution. `CO` can be estimated by this method.

`5CO + I_2O_5 rightarrow I_2 + 5CO_2`

(ii) `CO` does not support combustion but itself burns in air with a blue flame producing carbon suboxide.

Tests of carbon monoxide :

(i) It bums with blue flame.

(ii) Filter paper soaked with `PdCl_2` is turned pink, green or black. `PdCl_2` is reduced to the metal.

(iii) It reduces iodine pentaoxide into free iodine, which give colour with `C Cl_4`, `CS_2` or `CHCl_3`.

Preparation :

(i) By burning carbon, fossil fuels & other org. compounds in air

`C + O_2 rightarrow CO_2`

`CH_4 + 2O_2 rightarrow CO_2 + 2H_2O`

(ii) By action of `HCl` on carbonates (laboratory method)

`CaCO_3 + 2HCl overset(Delta) rightarrow CaCl_2 + CO_2 + H_2O`

`NaHCO_3 + HCl overset(Delta) rightarrow NaCl + H_2O + CO_2`

Physical Properties :

(i) Colourless & odourless gas (about `1.5` time heavier than air).

(ii) Not poisonous, but does not support life.

Chemical Properties :

(i) Non combustible nature (certain active metals `Na`, `K`, `Mg` burn in it).

`2Mg + CO_2 rightarrow 2MgO + C`

`Zn + CO rightarrow ZnO + CO`

(ii) Acidic nature : It dissolves in water to some extent to form carbonic acid.

`CO_2 + H_2O undersettext(carbonic acid) -> H_2CO_3 ⇋ H^(+) + HCO_3^-`

(weak dibasic acid)`2H^(+) + CO_3^(-2)`

It reacts with metallic oxides

`CaO + CO_2 rightarrow CaCO_3`

`Na_2O + CO_2 rightarrow Na_2CO_3`

(i) Structure : `O= C = C = C = O` (Linear)

Preparation :

By heating malonic acid with phosphorus pentaoxide.

`undersettext(malonic acid)[3(COOH-CH_2-COOH) + P_4O_(10) overset(150^oC) rightarrow 3C_3O_2 + 4H_3PO_4`


Properties :

(i) Colourless gas, B.P. = `60^oC`.

(ii) Very readily polymerises to give coloured salts.

(iii) It decomposes at `200^oC`.

`C_3O_2 overset(200^oC) rightarrow CO_2 + 2C`

(i) Oxyacids are formed by `C` & `Si`.

(ii) Main inorganic oxyacid is `H_2CO_3`

(iii) `H_2SiO_3` is silica acid.

(i) They form tetrahalides `MX_4` except `PbBr_4` & `PbI_4`.

(ii) The non existence of `PbBr_4` and `PbI_4` is due to that `Pb^(+4)` is a strong oxidising agent while `Br^(-)` & `I^-` are highly reducing agent.

(iii) All `MX_4` are covalent except `SnF_4`. lt is Ionic.

(iv) The tetrahalides of carbon cannot undergo hydrolysis due to non availability of vacant `d`-orbitals `C Cl_4 + H_2O rightarrow COCl_2 + 2HCl`.

(v) The tetrahalides of silicon like `SiF_4` can form `SiF_6^(2-)`. In this ion silicon undergoes `sp^3d^2` hydridisation where carbon cannot form this type of ion.

(vi) Dihalides of these elements are more ionic than their corresponding tetrahalides.

(vii) Thermal stability of tetrahalides

`CX_4 > SiX_4 > GeX_4 > SnX_4 > PbX_4`.