P Block Elements, Class 12, Chemistry Detailed Chapter Notes PDF Download

Group-III  - The p block elements, Chemistry, Class 12

p-block Elements

Group-III

Isolation of "B" :

(i) Preparation of B₂O₃ from Borax or Colemanite

Na₂B₄O₇ HCl / H₂SO₄ → H₂B₄O₇

H₂B₄O₇ 5H₂O → 4H₃BO₃ B₂O₃ H₂O

(ii) Reduction of B₂O₃

B₂O₃ Na / K / Mg / Al → B Na₂O / K₂O / MgO / Al₂O₃

 

Chemical Props. :

(i) Burning in air : 4B 3O₂ → 2B₂O₃

4Al 3O₂ → 2Al₂O₃

(ii) Reaction with water

B H₂O (Cold & Hot) → no reaction

2B 3H₂O → B₂O₃ H₂

                         (red hot)

Al 3H₂O → Al(OH)₃ 3/2 H₂

(iii) B HCl → no reaction

B H₂SO₄(dil.) → no reaction

2B 3H₂SO₄(conc.) → 2H₃BO₃ 3SO₂

B 3HNO₃ → H₃BO₃ 3NO₂

2Al 6H₂SO₄ → Al₂(SO₄)₃ 3SO₂ 6H₂O

Al HNO₃(80%) → Al₂O₃ (passive layer) and does not react further.

(iv) 2B 2NaOH 2H₂O → 2NaBO₂ 3H₂

2Al 2NaOH 2H₂O → 2NaAlO₂ 3H₂

(v) 2B N₂ → 2BN 2Al N₂ → 2AlN

4B C → B₄C 4Al 3C → Al₄C₃

(vi) 3Mg 2B → Mg₃B₂

Preparation of B₂H₆ :

(i) Mg₃B₂ HCl (10%) → B₂H₆ B₄H₁₀ B₅H₉ etc.

(ii) B₄H₁₀ B₂H₆ H₂ higher borane

(iii) BCl₃ (or BBr₃) 6H₂ B₂H₆ 6HCl

(iv) 3LiAlH₄ or (LiBH₄) 4BF₃ → 3LiF 3AlF₃ or 3(BF₃) 2B₂H₆

Reaction of B₂H₆ :

(i) B₂H₆ O₂ B₂O₃ H₂O

(ii) B₂H₆ H₂O (Cold is enough) → H₃BO₃ 6H₂

(iii) B₂H₆ HCl (dyr) B₂H₅Cl H₂

• Heating of Boric Acid :

H₃BO₃ HBO₂ H₂B₄O₇ B₂O₃

Metaboric acid Tetraboric acid Glassy mass

• H₃BO₃ H₂O₂ → (H₂O) (HO)₂B-O-O-H

Sodium peroxy borate used in washing

powder as whitener

Preparation of Borax :

2CaO·3B₂O₃ 2Na₂CO₃ → 2CaCO₃¯ Na₂B₄O₇ 2NaBO₂

Colemanite

[4NaBO₂ CO₂ → Na₂B₄O₇ Na₂CO₃

Na₂B₄O₇·10H ₂O¯

Uses of Borax :

(i) In making glass, enamel and gaze or pottery.

(ii) As antiseptics in medicinal soaps preparation.

Al₂O₃ preparation :

(i) 2Al(OH)₃ Al₂O₃ 3H₂O

(ii) Al₂(SO₄)₃ Al₂O₃ 3SO₃

(iii) (NH₄)₂SO₄· Al₂(SO₄)₃· 24H₂O Al₂O₃ 2NH₃ 4SO₃ 25H₂O

Uses : (i) In making refractory brick

(ii) as abrasive

(iii) To make high alumina cement

AlCl₃ Preparation :

(i) 2Al 6HCl(vap.) → 2AlCl₃ 3H₂

(over heated) (dry)

(ii) Al₂O₃ 3C 3Cl₂ 2AlCl₃ (vap.) 3CO

 

Solid anh. AlCl₃

Props :

(i) Its anhydrous formed is deliquescent and fumes in air.

(ii) It sublimes at 180ºC.

(iii) It is covalent and exists in the form of dimer even if in non polar solvents e.g. alc., ether, benzene, where it is soluble in fair extent.

Uses : (i) Friedel-Craft reaction

(ii) Dyeing, drug & perfumes etc.

 

Alumns : M₂SO₄, M'₂(SO₄)₃·24H ₂O Props : Swelling characteristics

where M = Na , K , Rb , Cs , As , Tl , NH₄

M' = Al ³, Cr ³, Fe ³, Mn ³, Co ³

K₂SO₄·Al₂ (SO₄)₃·24H₂ O Potash alum

(NH₄)₂SO₄· Al₂(SO₄)₃· 24H₂O Ammonium alum

K₂SO₄·Cr₂ (SO₄)₃·24H₂ O Chrome alum

(NH₄)₂SO₄· Fe₂(SO₄)₃· 24H₂O Ferric alum

Preparation :

Al₂O₃ 3H₂SO₄ → Al₂(SO₄)₃ 3H₂O

Al₂(SO₄)₃ K₂SO₄ aq. solution → crystallise

Uses : (i) Act as coagulant. (ii) Purification of water (iii) Tanning of leather

(iv) Mordant in dying (v) Antiseptic

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Group-IV - The p block elements, Chemistry, Class 12

Group-IV

Types of Carbide :

(i) Ionic and salt like

classification on basis of (a) C₁ unit

no. of carbon atoms (b) C₂ unit

present in hydrocarbon (c) C₃ unit

found on their hydrolysis

C₁ unit : Al₄C₃, Be₂C

Be₂C H₂O → Be(OH)₂ CH₄

Al₄C₃ 12H₂O → 4Al(OH)₃ 3CH₄

C₂ unit : CaC₂, BaC₂

CaC₂ 12H₂O → Ca(OH)₂ CH º CH

C₃ unit : Mg₂C₃

Mg₂C₃ H₂O → 2Mg(OH)₂ CH₃-C º CH : Propyne

(ii) Covalent carbinde : SiC & B₄C

(iii) Interstitial carbide : MC (Transition element or inner transitional elements forms this kind of carbide)

Interstitial carbide formation doesn't affect the metallic lusture and electrical conductivity. (no chemical bond is present, no change in property.)

SiC

Preparation : SiO₂ 2C(coke) Si 2CO­

Si C SiC diamond like structure colourless to yellow solid in room temp.

¯

when impurity is present

Properties :

(i) It is very hard and is used in cutting tools and abrassive powder (polishing material).

(ii) It is very much inert.

(iii) It is not being affected by any acid except H₃PO₄.

CO

- How to detect

- How to estimate

- What are its absorbers

(i) How to detect

(a) burns with blue flame.

(b) CO is passed through PdCl₂ solution giving rise to black ppt.

CO PdCl₂ H₂O → CO₂­ Pd¯ 2HCl

Black metallic deposition

(ii) How to estimate

I₂O₅ 5CO → I₂ 5CO₂

I₂ S₂O₃^2- → 2I^- S₄O₆^2-

(iii) What are its absorbers

(a) Cu₂Cl₂ : CuCl CO 2H₂O → [CuCl(CO)(H₂O)₂]

Uses :

In the Mond's process of Ni-extraction

CO is the purifying agent for Ni

Impure

Producer gas : CO N₂ H₂

Water gas : CO H₂

Water gas is higher calorific value than producer gas.

in water gas, both CO & H₂ burns while in producer gas N₂ doesn't burn.

Taflon

CHCl₃ HF CF₂HCl CF₂ = CF₂

Purpose

Temp. withstanding capacity upto 500-550ºC (1^st organic compound withstand this kind of high temperature.)

Silicon (Si)

Occurence :

Silicon is the second most abundant (27.2%) element after oxygen (45.5%) in the earth's crust. It does not occur free in nature but in the combined state, it occurs widely in form of silica and silicates. All mineral rocks, clays and soils are built of silicates of magnesium, aluminium, potassium or iron. Aluminium silicate is howeve the most common constituent of rocks and clays.

Silikca is found in the free state in sand, flint and quartz and in the combined state as silicates like

(i) Feldspar - K₂O.Al₂O₃.6SiO ₂

(ii) Kaolinite - Al₂O₃.2SiO₂.2H ₂O

(iii) Asbestos - CaO.3MgO.4SiO₂

Preparation :

(i) From silica (sand) : Elemental silicon is obtained by the reduction of silica (SiO₂) with high purity coke in an electric furnace.

SiO₂(s) 2C(s) Si(s) 2CO(g)

(ii) From silicon tetrachloride (SiCl₄) or silicon chloroform (SiHCl₃) : Silicon of very high purity required for making semiconductors is obtained by reduction of highly purified silicon tetrachloride or silicon chloroform with dihydrogen followed by purification by zone refining.

SiCl₄(l) 2H₂(g) → Si(s) 4HCl(g)

SiHCl₃(s) H₂(g) → Si(s) 3HCl(g)

Physical Properties :

(i) Elemental silicon is very hard having diamond like structure.

(ii) It has shining luster with a melting point of 1793 K and boiling point of about 3550 K.

(iii) Silicon exists in three isotopes, i.e. ₁₄Si²⁸, ₁₄Si²⁹ and ₁₄Si³⁰ but ₁₄Si²⁸ is the most common isotope.

Chemical Properties :

Silicon is particularly unreactive at room temperature towards most of the elements except fluorine. Some important chemical reactions of silicon are discussed below.

(i) Action of air : Silicon reacts with oxygen of air at 1173 K to form silicon dioxide and with nitrogen of air at 1673 K to form silicon nitride,

Si(s) O₂(g) SiO₂(s)

Silicon dioxide

3Si(s) 2N₂(g) Si₃N₄(s)

Silicon nitride

(ii) Action of steam : It is slowly attacked by steam when heated to redness liberating dihydrogen gas.

Si(s) 2H₂O(g) SiO₂(s) 2H₂(g)

(iii) Reaction with halogens : It burns spontaneously in fluorine gas at room temperature to form silicon tetrafluoride (SiF₄).

Si(s) 2F₂ SiF₄(l)

However, with other halogens, it combines at high temperature forming tetrahalides.

(iv) Reaction with carbon : Silicon combines with carbon at 2500ºC forming silicon carbide (SiC) known as carborundum.

Si(s) C(s) SiC(s)

Carborundum is an extremely hard substance next only to diamond. It is mainly used as an abrasive and as a refractory material.

 

Uses :

(i) Silicon is added to steel as such or more sually in form of ferrosilicon (an alloy of Fe and Si) to make it acid-resistant.

(ii) High purity silicon is used as semiconductors in electronic devices such as transistors.

(iii) It is used in the preparation of alloys such as silicon-bronze, magnesium silicon bronze and ferrosilicon.

Compounds of Silicon :

What is silane. Si_nH_{2n 2} SiH₄ & Si₂H₆

Only these two are found

Higher molecules are not formed. Si can't show catanetion property.

Hot Mg Si-vap → Mg₂Si MgSO₄ SiH₄ Si₂H₆ ......

Ques. SiH₄ is more reactive than CH₄. Explain.

Reasons :

(i) Si^d - H^d- in C^d- - H^d

C - electro -ve than H

Si less electro -ve than H

So bond polarity is reversed when Nu^- attacks, it faces repulsion in C but not in Si.

(ii) Silicon is having vacant d orbital which is not in case of carbon.

(iii) Silicon is larger in size compared to C. By which the incoming Nu^- doesn't face any steric hindrance to attack at Si whereas CH₄ is tightly held from all sides.

Silicones :

It is organo silicon polymer,

CCl₄ H₂O → no hydrolysis

but CCl₄ H₂O → COCl₂ 2HCl

super heated steam

SiCl₄ H₂O → Si(OH)₄ 4HCl

SiO₂(3-D silicate)

R₂SiCl₂ H₂O R₂Si(OH)₂

Linear silicone

R₂CCl₂ H₂O R₂C(OH)₂

Silicones may have the cyclic structure also having 3, 4, 5 and 6 nos. of silicon atoms within the ring. Alcohol analogue of silicon is known as silanol.

R₃SiCl R₃Si-O-SiR₃

R₂SiCl₂ R₃SiCl

* Using R₃SiCl in a certain proportion we can control the chain length of the polymer.

RSiCl₃ H₂O → R-Si(OH)₃

It provides the crosslinking among the chain making the polymer more hard and hence controling the proportion of RSiCl₃ we can control the hardness of polymer.

Uses :

(1) It can be used as electrical insulator (due to inertness of Si-O-Si bonds).

(2) It is used as water repellant ( surface is covered) eg. car polish, shoe polish, massonary work in buildings.

(3) It is used as antifoaming agent in sewage disposal, beer making and in cooking oil used to prepare potato chips.

(4) As a lubricant in the gear boxes.

Silica (SiO₂)

Occurrence :

Silica or silicon dioxide occurs in nature in the free state as sand, quartz and flint and in the combined state as silicates like, Feldspar : K₂O.Al₂O₃.6SiO ₂, Kaolinite : Al₂O₃.2SiO₂.2H ₂O etc.

Properties :

(i) Pure silica is colourless, but sand is usually coloured yellow or brown due to the presence of ferric oxide as an impurity.

(ii) Silicon dioxide is insoluble in water and all acids except hydrofluoric acid.

SiO₂(s) 4HF(l) → SiF₄(l) 2H₂O(l)

(iii) It also combines with metallic oxides at high temperature giving silicates e.g.,

SiO₂(s) CaO(s) CaSiO₃(s)

 

(iv) When silica is heated strongly with metallic salts, silicates are formed and the volatile oxides are driven off as vapours.

SiO₂(s) Na₂CO₃(s) Na₂SiO₃(s) CO₂(g)

SiO₂(s) Na₂SO₄(s) Na₂SiO₃(s) CO₃(g)

3SiO₂(s) Ca₃(PO₄)₂(s) 3CaSiO₃(s) P₂O₅(g)

The first two examples quoted here are important in glass making.

Structure of Silica :

Silica has a three-dimensional network structure. In silica, silicon is sp³-hybridized and in thus linked to four oxygen atoms and each oxygen atom is linked to two silicon atoms forming a three-dimensional giant molecule as shown in figure. This three-dimensional network structure imparts stability to SiO₂ crystal and hence a large amount of energy is required to break the crystal resulting in high melting point.

Uses :

(i) Sand is used in large quantities to make mortar and cement.

(ii) Being transparent to ultraviolet light, large crystal of quartz are used for making lenses for optical instruments and for controlling the frequency of radio-transmitters.

(iii) Powdered quartz is used for making silica bricks.

(iv) Silica gel (SiO₂.xH₂O) is used as a desiccant (for absorbing moisture) and as an absorbent in chromatography.

Tin & Its Compound

(i) [Burns with a bright flame]

(ii) Sn 2H₂O

(iii) Reaction with acid,

(iv) Sn 2NaOH H₂O → Na₂SnO₃ 2H₂­.

or

KOH [In absence of air Na₂SnO₂ forms and in contact with air it readily converts into Na₂SnO₃.]

Oxides : SnO(grey) & SnO₂(white)

Both are amphoteric in nature :

SnO H₂SO₄ → SnSO₄ H₂O

SnO 2HCl → SnCl₂ H₂O

SnO 2NaOH or KOH Na₂SnO₂ or K₂SnO₂ H₂O

But conc. hot alkali behaves differently.

2SnO 2KOH or NaOH → K₂SnO₃ or Na₂SnO₃ Sn H₂O

Bi(OH)₃ [Sn(OH)₄]^2- → Bi¯ [Sn(OH)₆]^2-

(black)

SnO₂ 2H₂SO₄ Sn(SO₄)₂ 2H₂O

(Soluble only in hot conc. H₂SO₄)

SnO₂ 2NaOH → Na₂SnO₃ H₂O

SnCl₂ & SnCl₄ :

(1) Sn 2HCl (hot conc.) → SnCl₂ H₂­

SnCl₂.2H₂O Sn(OH)Cl HCl­ H₂O­ Þ Hence anh. SnCl₂ cannot be obtained.

¯

SnO HCl­

{SnCl₄ 4H₂O → Sn(OH)₄ 4HCl­ fumes comes out}

(2) A piece of Sn is always added to preserved a solution of SnCl₂. Explain.

6SnCl₂ 2H₂O O₂ → 2SnCl₄ 4Sn(OH)Cl¯ (white ppt)

SnCl₄ Sn → 2SnCl₂

SnCl₄ 4H₂O → Sn(OH)₄¯ (white ppt.) 4HCl

(3) SnCl₂ HCl → HSnCl₃ H₂SnCl₄

SnCl₄ 2HCl → H₂SnCl₆ (Hexachloro stannic (IV) acid)

SnCl₄ 2NH₄Cl → (NH₄)₂SnCl₆ (colourless crystalline compound known as "pink salt")

(4) Red Prop. of SnCl₂ :

Sn ² 2Fe ³ → 2Fe ² Sn ⁴

2Cu² Sn ² → 2Cu Sn ⁴

Hg ² Sn ² → Hg¯ Sn ⁴

PhNO₂ SnCl₂ / HCl → PhNH₂ Sn ⁴

K₂Cr₂O₇ SnCl₂ HCl → Cr ³ Sn ⁴ KCl H₂O

(5) Readily combines with I₂ Þ SnCl₂I₂ Þ This reaction is used to estimate tin.

Formation of SnCl₄ :

(i) Sn Cl₂(Excess) → SnCl₄

(molten) (dry)

(ii) 2HgCl₂ SnCl₂ → 2Hg¯ SnCl₄

(iii) Sn Aq. rigia → SnCl₄ NO H₂O

SnCl₄.5H₂O is known as butter of tin Þ used as mordant.

(NH₄)₂SnCl₆ is known as `pink salt' Þ used as calico printing.

Mosaic gold : SnS₂ yellow crystalline substance :

Sn 4NH₄Cl → (NH₄)₂SnCl₄ 2NH₃ H₂

2(NH₄)₂SnCl₄ 2S → SnS₂ 2NH₄Cl (NH₄)₂SnCl₆

Distinction of Sn ² / Sn ⁴ :

(i) H₂S (ii) Hg ² (iii) Fe ³ K₃[Fe(CN)₆ Blue ppt.

Compound of Lead

Oxides of Lead :.

(i) PbO (ii) Pb₃O₄ (Red) (iii) Pb₂O₃ (reddish yellow) (Sesquioxide)

(iv) PbO₂ (dark brown)

(1)

Laboratory Preparation :

Pb(NO₃)₂ → 2PbO 4NO₂ O₂

PbO₂

Pb₃O₄ →

Pb₂O₃ →

Preparation of Pb₂O₃ :

2PbO NaOCl → Pb₂O₃ NaCl

Pb₂O₃ 2HNO₃ → PbO₂¯ Pb(NO₃)₂ H₂O

This reaction suggest that Pb₂O₃ contains PbO₂.

(2) Pb₃O₄ : 6PbO O₂ 2Pb₃O₄ (In the same way, prove that its formula is 2PbO.PbO₂)

Pb₃O₄ 4HNO₃ (cold. conc.) or (hot dil.) → 2Pb(NO₃)₂ PbO₂ 2H₂O

But 2Pb₃O₄ 6H₂SO₄ 6PbSO₄ 6H₂O O₂

Pb₃O₄ 8HCl → 3PbCl₂ 4H₂O Cl₂

(3) PbO₂ : Insoluble in water. HNO₃, But reacts with HCl H₂SO₄ (hot conc.) and in hot NaOH/ KOH.

(i) Pb₃O₄ 4HNO₃ → 2Pb(NO₃)₂ PbO₂ 2H₂O

(ii) Pb(OAc)₂ Ca(OCl)Cl H₂O → PbO₂ [Brown (dark)] CaCl₂ 2CH₃CO₂H

¯

Excess bleaching powder is being removed by stirring with HNO₃.

Reaction : PbO₂ 4HCl → PbCl₂ Cl₂ 2H₂O

2PbO₂ 2H₂SO₄ 2PbSO₄ 2H₂O O₂

PbO₂ 2NaOH → Na₂PbO₃ H₂O

PbO₂ : Powerful oxidising agent :

(i) PbO₂ SO₂ → PbSO₄ [spontaneously]

(ii) PbO₂ 2HNO₃ (COOH)₂ → Pb(NO₃)₂ 2CO₂ 2H₂O

(iii) 2Mn(NO₃)₂ 5PbO₂ 6HNO₃ → 3Pb(NO₃)₂ 2PbSO₄¯ 2HMnO₄ 2H₂O

PbCl₄ : Exists as H₂[PbCl₆]

PbO₂ 4HCl → PbCl₄ 2H₂O

{ice cold conc. saturated with Cl₂}

PbCl₄ 2HCl → H₂PbCl₆

TetraEthyl lead :

4Na-Pb (alloy 10%-Na) 4C₂H₅Cl (vap.) → 3Pb Pb(Et)₄ 4NaCl

It is antiknocking agent.

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Group - V - The p block elements, Chemistry, Class 12

Group - V

Preparation of N₂ :

(i) NH₄NO₂ N₂ 2H₂O

(ii) (NH₄)₂Cr₂O₇ N₂ 4H₂O Cr₂O₃

(iii) Ba(N₃)₂ Ba 3N₂

2NaN₃ 2Na 3N₂

(iv) 2NH₃ 3NaOCl → N₂ 3NaCl 3H₂O

(v) 2NO 2Cu → 2CuO N₂

(red, overheated) (Black)

(vi) Cl₂ passed into liquor NH₃

3Cl₂ 2NH₃ → N₂ 6HCl

6NH₃ 6HCl → 6NH₄Cl

----------------------------------------------------

3Cl₂ 8NH₃ → N₂ 6NH₄Cl

In this method NH₃ conc. should not be lowered down beyond a particular limit.

3Cl₂ NH₃ → NCl₃ 3HCl

(Tremendously explosive)

Properties of N₂ :

(i) It is inert due to high bond energy.

(ii) It is absorbed by hot metal like Ca, Mg, Al etc.

3Ca N₂ → Ca₃N₂

Bright hot 2Al N₂ → 2AlN

Al₂O₃ 3C N₂ 2AlN 3CO

(BN)_x : Inorganic graphite

White slippery solid having 2D-sheet structure.

(BN)_x (BN)_x

3-D network structure similar to diamond (Borazon) which is harder than diamond and used for diamond cutting.

Na₂B₄O₇ 2NH₄Cl 2NaCl 2NH₃ 2B₂O₃ H₂O

B₂O₃ 2NH₃ → 2BN 3H₂O

(iii) N₂ can be absorbed by calcium carbide at the temp around 1000ºC, CaC₂

it is a very good fertiliser.

Cyanamide ion :

(iv)

Types of Nitride :

(i) Salt like or ionic : Li₃N, Na₃N, K₃N (?), Ca₃N₂, Mg₃N₂, Be₃N₂

(ii) Covalent : AlN, BN, Si₃N₄, Ge₃N₄, Sn₃N₄

(iii) Interstitial : MN

No of metal atom per unit cell is equal to no of octahedral voids per unit cell.

All the octahedral voids are occupied by nitrogen atoms. Hence the formula is MN.

HCP : Hexagonal closed pack FCC : Face centred cubic

NH₃ preparation :

(i) Nitrate or nitrite reduction : NO₃^- / NO₂^- Zn or Al NaOH → NH₃ [Zn(OH)₄]^2- or [Al(OH)₄]^-

(ii) Metal nitride hydrolysis : N^3- 3H₂O → NH₃­ 3OH^-

(iii) Haber's process : N₂ 3H₂ 2NH₃

 

Q.1 NH₃ can't be dried by H₂SO₄, P₂O₅ and anh. CaCl₂ because :

2NH₃ H₂SO₄ → (NH₄)₂SO₄

H₂O NH₃ P₂O₅ → (NH₄)₃PO₄

CaCl₂ 8NH₃ → CaCl₂.8NH₃

forms adduct

Quick lime is used for this purpose

Properties :

(i) It dissolves several electropositive metals like Li, Na, K, Rb, Cs, Sr, Ba etc.

Eg. : K in liq NH₃ Þ (i) Blue in colour

(ii) Conducts electricity

(iii) having reducing property

K₂[Ni(CN)₄ K₄[Ni(CN)₄]

Square planar Tetrahedral

complex complex

(ii) Ag(NO₃)(aq) BaCl₂(aq) → AgCl ¯ Ba(NO₃)₂

(iii) CH₃COOH is strong acid in liq. NH₃ while in water is weak acid.

NH₃ H → NH₄ H₂O H → H₃O

Basisity order NH₃ > H₂O

more solvation of H in NH₃.

(iv) Hydrolysis and Ammonolysis occurs is a same way.

SiCl₄ 4H₂O → 4HCl Si(OH)₄ SiO₂ 2H₂O

SiCl₄ 8NH₃ → 4NH₄Cl Si(NH₂)₄ Si₃N₄ NH₃­

Rate of hydrolysis and Ammonolysis will be affected by the presence of HCl vapour & NH₄Cl vapour respectively.

NH₄ - Salts Preparation

Oxides of Nitrogen :

Oxides of Nitrogen Structure Physical state colour of gas

N₂O Gas Colourless

NO or Gas Colourless

N₂O₃ Gas Blue liquid (-30ºC)

NO₂ Gas Brown

N₂O₅ Colourless solid -(no existance in gas phase)

Preparations :

1. N₂O :

(i) NH₄NO₃ → N₂O H₂O

(ii) (NH₄)₂SO₄ NaNO₃ → NH₄NO₃ Na₂SO₄

¯

N₂O 2H₂O

(iii) Zn HNO₃ → Zn(NO₃)₂ N₂O H₂O

(dil.&Cold)

2. NO :

(i) Cu HNO₃ (1 : 1) → Cu(NO₃)₂ NO H₂O

hot

(ii) KNO₃ FeSO₄ H₂SO₄ → Fe₂(SO₄)₃ K₂SO₄ NO H₂O

FeSO₄ NO → FeSO₄ . NO FeSO₄ NO­

(iii) Ostwald process - Restricted oxidation of NH₃.

Industrial process :

4NH₃ 5O₂ 4NO 6H₂O

3. N₂O₃ :

(i) HNO₃ As₂O₃ → H₃AsO₄ N₂O₃

(ii) Cu HNO₃(6M) → Cu(NO₃)₂

4. NO₂ :

(i) M(NO₃)₂ MO 2NO₂ 1/2O₂ [M = Pb, Cu, Ba, Ca]

(ii) (Cu, Pb, Ag) HNO₃ → M-nitrate NO₂ H₂O

Hot & Conc.

5. N₂O₅ :

(i) 2HNO₃ P₂O₅ → 2HPO₃ N₂O₅

(ii) 4AgNO₃ 2Cl₂(dry gas) → 4AgCl 2N₂O₅ O₂

Properties :

(I) Decomposition Behaviour :

(i) N₂O 2N₂ O₂

(ii) 2NO N₂ O₂

(iii) N₂O₃ NO₂ NO

(Blue liq.) at (-30º C)

(iv) 2NO₂ 2NO O₂

N₂O₄ 2NO₂

(white solid) Brown gas

at (-11ºC)

(v) N₂O₄ N₂O₅ 2NO₂ 1/2O₂

colourless yellow

solid liq.

(II) Reaction with H₂O & NaOH :

H₂O NaOH

(i) N₂O : Fairly soluble in water and

produces neutral solution .............

(ii) NO : Sparingly soluble in water

and produces neutral solution ............

(iii) N₂O₃ : 2HNO₂

Hence it is known as

anhydride of HNO₂ NaNO₂

(iv) NO₂ : HNO₂ HNO₃

called as mixed anhydride NaNO₂ NaNO₃

(v) N₂O₅ : 2HNO₃

called as anhydride of HNO₃ NaNO₃

Other properties :

N₂O : 2N₂O → 2N₂ O₂

Hence it is better supporter

for combustion

S N₂O → SO₂ N₂

P N₂O → P₂O₅ N₂

Mg N₂O → MgO N₂

Na N₂O → Na₂O N₂

Cu N₂O → CuO N₂

H₂ N₂O → H₂O N₂

NO : (i) It burns : NO 1/2 O₂ → NO₂

(ii) It supports combustion also for molten sulphur and hot phosphorous.

S 2NO → SO₂ N₂

2P 5NO → P₂O₅ 5/2 N₂

(iii) It is being absorbed by FeSO₄ solution.

(iv) It is having reducing property.

KMnO₄ NO H₂SO₄ → K₂SO₄ MnSO₄ HNO₃ H₂O

HOCl NO H₂O → HNO₃ HCl

(v) NO shows oxidising property also.

SO₂ 2NO H₂O → H₂SO₄ N₂O

H₂S 2NO → H₂O S¯ N₂O

3SnCl₂ 2NO 6HCl → 3SnCl₄ 2NH₂OH

(Used for NH₂OH) preparation)

(vi) NO combines with X₂ (X₂ = Cl₂Br₂F₂) to produce NO X.

2NO X₂ → 2NOX

N₂O₃ : No more properties.

NO₂ : (1) It is having oxidising property.

S NO₂ → SO₂ NO

P NO₂ → P₂O₅ NO

C NO₂ → CO₂ NO

SO₂ NO₂ H₂O → H₂SO₄ NO

H₂S NO₂ → H₂O S¯ NO

CO NO₂ → CO₂ NO

NO not formed : 2KI 2NO₂ → I₂ 2KNO₂

(2) Reducing property of NO₂.

KMnO₄ NO₂ H₂SO₄ → K₂SO₄ MnSO₄ HNO₃ H₂O

N₂O₅ : I₂ 5N₂O₅ → I₂O₅ 10NO₂ (I₂O₅ is used for the estimation of CO)

I₂O₅ 5CO → I₂ 5CO₂

I₂ 2S₂O₃^2- → 2I^- S₄O₆^2-

N₂O₅ NaCl → NaNO₃ NO₂Cl

It proves that N₂O₅ is consisting of ion pair of NO₂ & NO₃^-.

Oxyacids of N :

HNO₂ : Preparation

(i) M-nitrite HNO₂

(ii) N₂O₃ H₂O → 2HNO₂

Properties :

(i) Oxidising property of HNO₂

KI HNO₂ HCl → KCl H₂O NO I₂

SnCl₂ HNO₂ HCl → SnCl₄ NO H₂O

SO₂ HNO₂ H₂O → H₂SO₄ NO

H₂S HNO₂ → H₂O S¯ NO

FeSO₄ HNO₂ H₂SO₄ → Fe₂(SO₄)₃ NO H₂O

Na₃AsO₃ HNO₂ → Na₂AsO₄ NO H₂O

(ii) Reducing property of HNO₂

KMnO₄ HNO₂ H₂SO₄ → K₂SO₄ MnSO₄ HNO₃ H₂O

K₂Cr₂O₇ HNO₂ H₂SO₄ → K₂SO₄ Cr₂(SO₄)₃ HNO₃ H₂O

H₂O₂ HNO₂ → H₂O HNO₃

HNO₂ urea →

thiourea →

sulphamic acid →

NH₃ → NH₄NO₂

C₂H₅NH₂ → C₂H₅OH N₂

Ph-NH₂ PhN₂ X^-

nitric acid (HNO₃)

1. It was named aqua forties (means strong water) by alchemists.

Preparation

(i) Laboratory Method

KNO₃ conc. H₂SO₄ KHSO₄ HNO₃(vap)

 

vapour of nitric acid evolved are condensed in a glass receiver.

(ii) Industrial Preparation

(A) Birkeland Eyde Process or arc process

Step 1 N₂ O₂ 2NO - heat

Step 2 NO O₂ NO₂

Step 3 NO₂ H₂O HNO₂ HNO₃

Step 4 HNO₂ HNO₃ NO H₂O

(B) Ostwald's Process

Step 1 NH₃ O₂ NO H₂O heat

Step 2 NO O₂ NO₂

Step 3 NO₂ H₂O HNO₂ HNO₃

Step 4 HNO₂ HNO₃ NO H₂O

PROPERTIES

Physical

Nitric acid usually acquires yellow colour due to its decomposition by sunlight into NO₂.

4HNO₃ 4 NO₂ 2H₂O O₂

The yellow colour of the acid can be removed by warming it to 60-80ºC and bubbling dry air through it.

It has extremely corrosive action on the skin and causes painful sores.

Chemical

(a) It is very strong acid. It exhibits usual properties of acids. It reacts with basic oxides, carbonates, bicarbonates and hydroxides forming corresponding salts.

CaO 2HNO₃ Ca(NO₃)₂ H₂O

Na₂CO₃ 2HNO₃ 2NaNO₃ H₂O CO₂

NaOH HNO₃ NaNO₃ H₂O

(b) Oxidising nature : Nitric acid acts as a strong oxidising agent as it decomposes to give nascent oxygen easily.

2HNO₃ H₂O 2NO₂ O

or 2HNO₃ H₂O 2NO 3O

(i) Oxidation of non- metals : The nascent oxygen oxidises various non - metals to their corresponding highest oxyacids.

(1) Sulphur is oxidised to sulphuric acid

(2) Carbon is oxidised to carbonic acid

C 4HNO₃ H₂CO₃ 4NO₂ 2H₂O

(3) Phosphorus is oxidised to orthophosphoric acid.

2P 10HNO₃ 2H₃PO₄ 10NO₂ 2H₂O

^{conc. and hot}

(4) Iodine is oxidised to iodic acid

I₂ 10HNO₃ 2HIO₃ 10NO₂ 4H₂O

^{conc. and hot}

(ii) Oxidation of metalloids

Metalloids like non-metals also form highest oxyacids

(1) Arsenic is oxidised to arsenic acid

2As 10HNO₃ 2H₃AsO₄ 10NO₂ 2H₂O

or As 5HNO₃ H₃AsO₄ 5NO₂ H₂O

^{conc. and hot}

(2) Antimony is oxidised to antimonic acid

Sb 5HNO₃ H₃SbO₄ 5NO₂ H₂O

^{conc. and hot}

(3) Tin is oxidised to meta - stannic acid.

Sn 2HNO₃ H₂SnO₃ 4NO₂ H₂O

(iii) Oxidation of compounds :

(1) Sulphur dioxide is oxidised to sulphuric acid

SO₂ 2HNO₃ H₂SO₄ 2NO₂

(2) Hydrogen sulphide is oxidised to sulphur

H₂S 2HNO₃ 2NO₂ 2H₂O S

(3) Ferrous sulphate is oxidised to ferric sulphate in presence of H₂SO₄

6FeSO₄ 3H₂SO₄ 2HNO₃ 3Fe₂(SO₄)₃ 2NO 4H₂O

(4) Iodine is liberated from KI.

6KI 8HNO₃ 6KNO₃ 2NO 3I₂ 4H₂O

(5) HBr, HI are oxidised to Br₂ and I₂, respectively.

2HBr 2HNO₃ Br₂ 2NO₂ 2H₂O

Similarly, 2HI 2HNO₃ I₂ 2NO₂ 2H₂O

(6) Ferrous sulphide is oxidised to ferrous sulphate

FeS HNO₃ Fe₂(SO₄)₃ 8NO₂ 4H₂O

(7) Stannous chloride is oxidised to stannic chloride is presence of HCl.

2HNO₃ 14H NH₂OH NH₃ 5H₂O

Hydroxylamine

NH₃ HNO₃ NH₄NO₃

------------------------------------------------------------------------

7SnCl₂ 14HCl 3HNO₃ 7SnCl₄ NH₂OH NH₄NO₃ 5H₂O

(8) Cane sugar is oxidised to oxalic acid.

C₁₂H₂₂O₁₁ 36HNO₃ 6(COOH)₂ 36NO₂ 23H₂O

(c) Action on Metals : Most of the metals will the exception of noble metals like gold and platinum are attacked by Nitric acid plays a double role in the action of metals, i,e, it acts as an acid as well as an oxidising agent. Amstrong postulated that primary action of nitric acid is to produce hydrogen in the nascent form. Before this hydrogen is allowed to escape, it reduces the nitric acid into number of products like NO₂, NO, H₂O, N₂ or NH₃ according to the following reactions :

Metal HNO₃ Nitrate H

2HNO₃ 2H 2NO 2H₂O

2HNO₃ 6H 2NO 4H₂O

2HNO₃ 10H N₂ 6H₂O

2HNO₃ 16H 2NH₃ 6H₂O

The progress of the reaction is controlled by a number of factors :

(a) the nature of the metal

(b) the concentration of the acid

(c) the temperature of the reaction

(d) the presence of other impurities.

------------------------------------------------------------------------------------------

Concentration of Metal Main Products

nitric acid

------------------------------------------------------------------------------------------

Very dilute HNO₃ (6%) Mg, Mn H₂ Metal nitrate

----------------------------------------------------------

Fe, Zn, Sn NH₄NO₃ metal nitrate H₂O

------------------------------------------------------------------------------------------

Dilute HNO₃ (20%) Pb, Cu, Ag, Hg NO metal nitrate H₂O

----------------------------------------------------------

Fe, Zn N₂O metal nitrate H₂O

----------------------------------------------------------

Sn NH₄NO₃ Sn(NO₃)₂

------------------------------------------------------------------------------------------

Conc. HNO₃(70%) Zn, Fe, Pb, Cu, Ag NO₂ metal nitrate H₂O

----------------------------------------------------------

Sn NO₂ H₂SnO₃

Metastannic acid

------------------------------------------------------------------------------------------

Action on Proteins

(i) Nitric acid attacks proteins forming a yellow nitro compound called xanthoprotein. It, therefore, stains skin and renders wool yellow colour. This property is utilized for the test of proteins.

 

(ii) Oxidation A number of organic compounds are oxidised.

Sawdust catches fire when nitric acid is poured on it. Turpentine oil bursts into flames when treated with fuming nitric acid, Cane sugar is oxidised to oxalic acid. Toluene is oxidised to benzoic acid with dil. HNO₃.

Structure

Nitric acid is a monobasic acid, i.e., the molecule consist of one hdyroxyl group as it is formed by the hdyrolysis of nitryl chloride, NO₂Cl. It may be structurally represented as bellow :

Gaseous nitric acid is a planar molecule. The bond lengths and bond angles as present in the molecule

are represented in the figure :

PHOSPHOROUS

INTERCONVERSION OF WHITE `P' & RED `p'

PREPARATION OF WHITE `P'

(i)

(ii) Ca₃(PO₄)₂ 3H₂SO₄ (conc.) 3CaSO₄ 2H₃PO₄

H₃PO₄ HPO₃

meta phosphoric acid

12C 4HPO₃ 2H₂ 12CO P₄

Coke white `P'

REACTIONS OF `P'

. P H₂SO₄ (hot & conc.) H₃PO₄ SO₂ H₂O

P KIO₃ H₂SO₄ H₃PO₄ I₂ K₂SO₄

. Reaction with hot metal -

3Na P Na₃P

3Mg 2P Mg₃P₂

3Ca 2P Ca₃P₂

2Cu 2P Cu₃P₂

Al P AIP

Ca₃P₂ H₂O M(OH)_n PH₃

or Mg₃P₂

or AIP

 

PREPARATION OF PH₃ (PHOSPHINE GAS)

 

(i) 4H₃PO₃ PH₃ 2H₃PO₄

PHYSICAL PROPERTIES

(i) It is having rotten fish smell

(ii) It is soluble in CS₂ and insoluble in water.

(NH₃ is soluble in water)

is formed with acids

PH₃ can be absorbed by Ca(OCl)Cl.

PH₃ 3Ca(OCl)Cl 3H₂O PCl₃ 3HCl 3Ca(OH)₂

2NH₃ 3Ca(OCl)Cl N₂ 3CaCl₂ 3H₂O

OTHER REACTIONS OF PH₃

(i) PH₃ O₂ P₂O₅ H₂O

(ii) PH₃ 3Cl₂ PCl₃ 3HCl

(iii) PH₃ 4N₂O H₃PO₄ 4N₂

(iv) 2PH₃ 3CuSO₄ Cu₃PO₂ 3H₂SO₄

Detection of PH₃ Black ppt.

(v) PH₃ 6AgNO₃ [Ag₃P .3AgNO₃] 3HNO₃

yellow ppt.

Ag₃P . 3AgNO₃ 3H₂O 6Ag 3HNO₃ H₃PO₃

Black ppt.

(vi) PH₃ 4HCHO HCl [P(CH₂OH)₄] Cl ^-

white/colourless solid

which is used for making

fire-proof cotton fabrics

 

EXAMPLE OF DEHYDRATING REACTION OF P₂O₅

HClO₃ P₂O₅ 2HPO₃ Cl₂O₇

H₂SO₄ P₂O₅ 2HPO₃ SO₃

HNO₃ P₂O₅ 2HPO₃ N₂O₅

_{===============================================================================}

GROUP VI - The p block elements, Chemistry, Class 12

GROUP VI

SULPHUR CHEMISTRY

Allotropes :

(iii) g-Sulphur

Amorphous forms are

(i) Plastic sulphur

(ii) Milk of sulphur

(iii) Colloidal sulphur

Viscosity of `S' with temperature

m.p. of `S' 112.8ºC

(i) > 112.8ºC to 160ºC slow decrease due to

S₈ rings slip and roll over one another easily.

(ii) > 160ºC, increases sharply due to breaking of

S₈ rings into chains and polymerises into large size chain.

(iii) 190ºC, again large chains are being broken into small chain.

* Milk of sulphur :

Powdered `S' Ca(OH)<sub>2</sub> suspension Solution Milk of `S'

12 S 3Ca(OH)₂ 2CaS₅ CaS₂O₃ 3H₂O

2CaS₅ CaS₂O₃ 6HCl 3CaCl₂ 12 S 3H₂O

* Colloidal Sulphur : Na₂S₂O₃ 2HCl 2NaCl H₂O SO₂ S

2H₂S SO₂ 3S 2H₂O

Props. of `S'

(a) Thin Cu-strip catches fire in sulphur vapour.

Cu S CuS.

(b) `S' burns spontaneously in fluorine. S 3F₂ SF₆

Cl₂ passed into liq. sulphur 2 S Cl₂ S₂Cl₂

(c) S 2H₂SO₄ 3SO₂ 2H₂O

S 2HNO₃ H₂SO₄ 2NO

(d) 4 S 6 KOH 2K₂S K₂S₂O₃ 3H₂O

(e) Burns in air : S O₂ SO₂

H₂S :

Prepⁿ :

FeS dil. H₂SO₄ FeSO₄ H₂S

FeS dil. HCl FeCl₂ H₂S

Sb₂S₃ (conc.) 6HCl 2SbCl₃ 3H₂S

Drying agent for this gas : fused CaCl₂, Al₂O₃ (dehydrated)

P₂O₅ etc. But not H₂SO₄, because

H₂SO₄ H₂S 2H₂O SO₂ S

Reducing property of H₂S :

Cl₂ H₂S 2HCl S

I₂ H₂S 2HI S

H₂O₂ H₂S 2H₂O S

SO₂ 2H₂S 2H₂O 3 S

2FeCl₃ H₂S 2FeCl₂ 2HCl S

4H₂O 4Cl₂ H₂S H₂SO₄ 8HCl

KMnO₄ H₂S H₂SO₄ S Mn²

H₂Cr₂O₇ H₂S H₂SO₄ Cr³ S

HNO₃ H₂S S NO₂ H₂O

With metal (hot)

2Na H₂S Na₂S H₂

Cu H₂S CuS H₂

Pb H₂S PbS H₂

With metal oxide (hot)

CaO H₂S CaS H₂O

ZnO H₂S ZnS H₂O

Metal ion H₂S M-Sulphides

(i) Alkali-sulphide water soluble

(ii) Alkaline earth - sulphide sparingly soluble

(iii) Al₂S₃ & Cr₂S₃ 6H₂O Al(OH)₃ or Cr(OH)₃ 3H₂S

Test :

(i) Smell rotten egg.

(ii) Pb- Acetate paper - black

(iii) Purple colour when alk. Nitropruside H₂S

Absorbent :

NaOH , KOH , PbNO₃ solution

Pb(NO₃)₂ H₂S 2HNO₃ PbS (Black)

 

SO₂

Prep :

Industrial :

4FeS₂ 11O₂ 2Fe₂O₃ 8SO₂

2ZnS 3O₂ 2ZnO 2SO₂

Lab prepⁿ :

Cu 2H₂SO₄ (conc.) CuSO₄ 2H₂O SO₂

Hg H₂SO₄ HgSO₄ H₂O SO₂

2Ag H₂SO₄ Ag₂SO₄ H₂O SO₂

S 2H₂SO₄ 3SO₂ 2H₂O

(Charcoal) C 2H₂SO₄ CO₂ 2SO₂ 2H₂O

NaHSO₃ H₂SO₄ NaHSO₄ H₂O SO₂

Props :

(i) Incombustible gas, but heated K burns in SO₂

4K 3SO₂ K₂SO₃ K₂S₂O₃

Reducing Prop.: (Revise from acid radical)

4FeCl₂ SO₂ 4HCl 4FeCl₃ H₂O S

6SnCl₂ 2SO₂ 8HCl 5SnCl₄ 4H₂O SnS₂ (Yellow solid)

(ii) SO₂ 2H₂SO₃ 2H₂SO₄ S

FeSO₄ Fe₂O₃ SO₂ SO₃

Fe₂(SO₄)₃ Fe₂O₃ 3SO₃

H₂SO₄ & SO₃ :

H₂SO₄ 2PCl₅ ........ SO₂Cl₂ 2POCl₃ 2HCl

Use of H₂SO₄ as nitrating mixture : good chlorinating agent

** P₂O₅ is stronger dehydrating agent than H₂SO₄ : H₂SO₄ P₂O₅ 2HPO3 SO₃

Properties of H₂SO₄ :

(a) Dissociation : At 444ºC. H₂SO₄ H₂O SO₃

(b) Acidic nature : NaOH H₂SO₄ H₂O Na₂SO₄ H₂O

(c) CO₃^2- H₂SO₄ SO₄^2- H₂O CO₂

HCO₃ H₂SO₄ H₃SO₄^- H₂O CO₂

 

(d) Zn / Fe H₂SO₄ ZnSO₄ & FeSO₄ H₂

where as

Cu 2H₂SO₄ CuSO₄ SO₂ 2H₂O

2Ag 2H₂SO₄ Ag₂SO₄ SO₂ 2H₂O

Hg 2H₂SO₄ HgSO₄ SO₂ 2H₂O

(e)

(f) Oxidising Prop. :

HBr / HI H₂SO₄ I₂/Cl₂ SO₂ H₂O

C 2H₂SO₄ CO₂ 2SO₂ 2H₂O

S 2H₂SO₄ 3SO₂ 2H₂O

2P 5H₂SO₄ H₃PO₄ 5SO₂

(g) Dehydrating agent :

 

C₆H₁₂O₆ 6 C

(COOH)₂ CO CO₂ PhH Ph - SO₃H

HCO₂H CO

SODIUM THIOSULPHATE

Propⁿ". :

(i) Na₂SO₃solⁿ S (powder) Na₂S₂O₃ Na₂S₂O₃.5H₂ O, monoclinic crystal

(ii)

(iii) 2Na₂S Na₂CO₃ 4SO₂ 3Na₂S₂O₃ CO₂

(iv) 6NaOH 4S Na₂S₂O₃ 2Na₂S 3H₂O

3Ca(OH)₂ 12 S CaS₂O₃ 3H₂O 2CaS₅

(v) Na₂SO₃ Na₂S I₂ Na₂S₂O₃ 2NaI

(vi) 2Na₂S 2O₂ H₂O Na₂S₂O₃ 2NaOH [Na₂S is readily oxidised in air giving rise to Na₂S₂O₃]

Props : (i) 4Na₂S₂O₃ Na₂S₅ 3Na₂SO₄

(ii) Na₂S₂O₃ 2H H₂S₂O₃ H₂O SO₂ S (White turbidity)

Reaction :

(i) Na₂S₂O₃ I₂ S₄O₆^2- 2I^-

Cl₂ - water SO₄^2- S 2HCl

Br₂ - water SO₄^2- S 2HBr

4OI^- 2OH^- 2SO₄^2- 4I^- H₂O

4Cl₂ 5H₂O Na₂SO₄ 8HCl H₂SO₄

(excess)

OZONE

Unstable deep blue, diamagnetic gas, with fishy smell. Toxic enough (more toxic than KCN). It's intense blue colour is due to the absorption of red light.

Oxidising property of O₃

It is one of best oxidising agent in acid solution. Its standard reduction potential value is 2.07 V.

O₃ 2H 2e O₂ H₂O Eº = 2.07 V

It is next to F₂. [above 2.07 V, only F₂, F₂O are there ]

(i) Metal Sulphides to Sulphates.

MS 4O₃ MSO₄ 4O₂ [M = Pb, Cu, Zn, Cd]

(ii) 2HX O₃ X₂ H₂O O₂ [X = Cl, Br, I]

(iii) NaNO₂ O₃ NaNO₃ O₂

Na₂SO₃ O₃ Na₂SO₄ O₂

Na₂AsO₃ O₃ Na₂AsO₄ O₂

(iv) Moist S, P, As O₃

S H₂O 3O₃ H₂SO₄ 3O₂

2P 3H₂O 5O₃ 2H₃PO₄ 5O₂

2As 3H₂O 5O₃ 2H₃AsO₄ 5O₂

(v) Moist I₂ HIO₃ whereas dry iodine I₄O₉ (yellow)

I₂ 5O₃ H₂O 2HIO₃ 5O₂

2I₂ 9O₃ I₄O₉ 9O₂

(vi) 2K₂MnO₄ O₃ H₂O 2KMnO₄ 2KOH O₂

2K₄[Fe(CN)₆] O₃ H₂O 2K₃[Fe(CN)₆] 2KOH O₂

2FeSO₄ O₃ H₂SO₄ Fe₂(SO₄)₃ O₂ H₂O

(vii)(a) 2KI (acidified) O₃ 2HCl I₂ 2KCl H₂O O₂

(b)

(c) alk.

(viii) Hg loses its fluidity (tailing of Hg)

2Hg O₃ Hg₂O O₂

similarly 2Ag O₃ Ag₂O O₂

Brown

(ix) BaO₂ O₃ BaO 2O₂

H₂O₂ O₃ H₂O 2O₂

Na₂O₂ O₃ H₂O 2NaOH 2O₂

(x) 2KOH 5O₃ 2KO₃ 5O₂ H₂O

In all above reaction O₃ gives up O₂ but some reactions are there which consumes all O-atom

(i) 3SO₂ O₂ 3SO₃

(ii) 3SnCl₂ 6HCl O₃ 3SnCl₄ 3H₂O

Absorbent :

(i) Turpentine oil

(ii) Oil of cinnamon

test :

(i) Sterilising water

(ii) Detection of position of the double bond in the unsaturated compound.

H₂O₂

Method preparation :

(i) Na₂O₂ H₂O (ice cold water) 2NaOH H₂O₂

(ii) BaO₂ H₂SO₄ BaSO₄ H₂O₂

Instead of H₂SO₄, H₃PO₄ is added now -a - days because H₂SO₄ catalyses the decomposition of H₂O₂ whereas H₃PO₄ favours to restore it.

3BaO₂ 2H₃PO₄ Ba₃(PO₄)₂ 3H₂O₂ and Ba₃(PO₄)₂ 3H₂SO₄ 3BaSO₄ 2H₃PO₄ (reused again)

(iii) Electrolysis of 50% H₂SO₄ using high current density.

2H₂SO₄ 2H 2H₂SO₄^-

2H₂SO₄^- H₂S₂O₈ 2e. [At anode] [At cathode 2H 2e H₂]

H₂S₂O₈ 2H₂O 2H₂SO₄ H₂O₂

(iv)

Properties :

(i) Colourless, odourless liquid (b.p. 152º)

(ii) Acidic nature :

H₂O₂ 2NaOH Na₂O₂ H₂O

H₂O₂ Ba(OH)₂ BaO₂ 2H₂O

H₂O₂ Na₂CO₃ Na₂O₂ CO₂ H₂O
 

(iii) It is oxidant as well as reductant.

H₂O₂ 2H 2e 2H₂O [reaction in acidic medium]

H₂O₂ 2e 2OH^- [reaction in alkali medium]

Oxidising Properties :

(i) PbS 4H₂O₂ PbSO₄ 4H₂O ( Used in washing of oil painting)

(ii) NaNO₂ H₂O₂ NaNO₃ H₂O

Na₂SO₃ H₂O₂ Na₂SO₄ H₂O

Na₃AsO₃ H₂O₂ Na₃AsO₄ H₂O

2KI H₂O₂ 2KOH I₂

H₂S H₂O₂ S 2H₂O

H₂SO₄ 2FeSO₄ H₂O₂ Fe₂(SO₄)₃ 2H₂O

2K₄[Fe(CN)₆] H₂O₂ H₂SO₄ 2K₃[Fe(CN)₆] K₂SO₄ 2H₂O

2[Cr(OH)₄]^- 3H₂O₂ 2OH^- 2CrO₄^2- 8H₂O

CrO₄^2- 2H H₂O₂ CrO₅ (Blue) 3H₂O

4CrO₅ 12H 4Cr ³ 7O₂ 6H₂O

Mn ² OH^- H₂O₂ MnO₂ 2H₂O This reaction can be utilised to detect NH₃

Reducing properties :

(a) Ag₂O H₂O₂ 2Ag H₂O O₂

(b) O₃ H₂O₂ H₂O 2O₂

(c) MnO₂ H₂O₂ H₂SO₄ MnSO₄ 2H₂O O₂

(d) PbO₂ H₂O₂ PbO H₂O O₂

(e) Pb₃O₄ 4HNO₃ 2Pb(NO₃)₂ PbO₂ 2H₂O

PbO₂ H₂O₂ PbO H₂O O₂

PbO 2HNO₃ Pb(NO₃)₂ H₂O

Pb₃O₄ H₂O₂ 6HNO₃ 3Pb(NO₃)₂ 4H₂O O₂

(f) X₂ H₂O₂ 2HX O₂ [X = Cl, Br]

2KMnO₄ 3H₂O 2KOH 2MnO₂ 2H₂O 3O₂

2MnO₄^- 2OH^- 2MnO₄^2- H₂O O

2MnO₄^2- 2H₂O 2MnO₂ 4OH^- 2O

2MnO₄^- H₂O 2MnO₂ 2OH^- 3O

(g) 2KMnO₄ 5H₂O₂ 3H₂SO₄ 2MnSO₄ K₂SO₄ 5O₂ 8H₂O

(h) 2[Fe(CN)₆]^3- 2OH^- H₂O₂ 2[Fe(CN)₆]^4- 2H₂O O₂

(i) NaOCl H₂O₂ NaCl H₂O O₂

(j) NaIO₄ H₂O₂ NaIO₃ H₂O O₂

Uses :

(i) As a rocket propellant :

NH₂.NH₂ 2H₂O₂ N₂ 4H₂O [highly exothemic and large increase in volume]

(ii) In detection of Cr ³, Ti ⁴ etc.

Ti(SO₄)₂ H₂O₂ 2H₂O H₂TiO₄ 2H₂SO₄

Yellow or orange

Pertitanic acid

================================================================

GROUP - VII - The p block elements, Chemistry, Class 12

GROUP - VII

HALOGENS

Method of Prep" :

F₂ : By electrolysis of KHF₂ (which is obtained from CaF₂)

CaF₂ H₂SO₄ CaSO₄ 2HF

HF KF KHF₂

KHF₂ H₂(at cathode) F₂ (at anode)

Cl₂ :

(i) By electrolysis of aq. NaCl

2NaCl 2H₂O

(ii) 2NaCl 2Na Cl₂

(Molten) (cathode) (anode)

(iii) In laboratory : Oxidising HCl by KMnO₄ or MnO₂

2KMnO₄ 16HCl 2KCl 2MnCl₂ 5Cl₂ 8H₂O

MnO₂ 4HCl MnCl₂ Cl₂ 2H₂O

Br₂ : From Bromine water (contains 65 ppm of Br^-)

Cl₂ 2Br^- 2Cl^- Br₂ (Br₂ is volatite in nature

Hence it is collected by

(i) removal of Br₂ vapour by stream of air.

(ii) absorbing it into Na₂CO₃ solution.

Br₂ 6OH^- Br^- BrO₃^- 3H₂O

Then acidified to get pure Br₂

5 Br^- BrO₃^- 6H 3Br₂ 3H₂O

I₂ : Chille salt petre contains traces ofNaIO₃ which is reduced to I^- by NaHSO₃, then oxidation of I^- to I₂ by IO₃^- .

2IO₃^- 6HSO₃^- 2I^- 6SO₄^2- 6H

5I^- IO₃^- 3I₂ 3H₂O

Q. Liquid I₂ conducts electricity. Explain

Ans. Due to its self ionisation 3I₂ I₃ I₃^-

Q. X₂ OH^- X^- OX^- H₂O but on acidification the disproportionated product gives

X^- XO₃^- H₂O back the same element.

X₂ = Cl₂, Br₂, I₂ But For F₂ i.e. X^- OX^- 2H X₂ H₂O

5X^- XO^-₃ 6H 3X₂ 2H₂O

2F₂ 2NaOH 2NaF F₂O H₂O X = Cl, Br, I

 

F₂O 2NaOH 2NaF O₂ H₂O

---------------------------------------

2F₂ 4NaOH 4NaF O₂ 2H₂O

HALOGEN ACID :

Acidity order : HI > HBr > HCl >> HF. (due to hydrogen bonding & less effective overlap with H atom)

Q. CaF₂ used in HF prepⁿ must be free from SiO₂. Explain

Ans. CaF₂ H₂SO₄ CaSO₄ HF

If SiO₂ present as impurity

Q. HF can not be stored in glass vessel. Explain.(same reason.)

Q. In the salt-cake method of prepⁿ. of HCl, NH₄Cl is being used instead of NaCl. Explain.

Ans. NaCl H₂SO₄ NaHSO₄ HCl

Insoluble

NaCl NaHSO₄ Na₂SO₄ HCl

(Salt Cake)

2NH₄Cl H₂SO₄ 2HCl (NH₄)₂SO₄

[NH₄HSO₄ intermediate is water soluble and easy to handle]

** Another altermative process to avoid the formation of NaHSO₄

Q. In the similar type of preparation of HBr and HI from bromide and iodide, H₂SO₄ can not be used and H₃PO₄ is used. Explain.

Ans. Since H₂SO₄ is an oxidising agent it oxidises HBr & HI to Br₂ and I₂ respectively.

2HBr H₂SO₄ Br₂ SO₂ 2H₂O

Hence, NaBr H₃PO₄ NaH₂PO₄ 3HBr

Another process ; PBr₃ 3H₂O H₃PO₄ 3HBr

Q. Boiling point order HX : HF > HI > HBr > HCl

Due to H-bonding

Q. HCl, H₂SO₄, HNO₃ are bases in liquid HF where as HClO₄ is acid. Comment.

Ans. HCl HF H₂Cl F^- ; H₂SO₄ HF H₃SO₄ F^-; HNO₃ HF H₂NO₃ P^-

But HClO₄ HF H₂F ClO₄^-

* HF is weak acid but addition of BF₃, AsF₅, PF₅, SbF₅ makes it strongly acidic. Explain

OXOACIDS :

HOF : H₂O F₂ HOF HF

 

HOX : very unstable becuase

it reacts with both H₂O

and F₂ as follows :

OX^- disproportionates in hot solution eg. 3OCl^- 2Cl^- ClO₃^-

X = Cl, Br, I

Bleaching Powder :

Prepⁿ. : Cl₂(g) Ca(OH)₂ Ca(OCl)Cl H₂O

Slaked lime

(a) On long standing it undergoes

(i) auto oxiation 6Ca(OCl)Cl Ca(ClO₃)₂ 5CaCl₂

(ii) 2Ca(OCl)Cl 2CaCl₂ O₂

(iii) Ca(OCl)Cl H₂O Ca(OH)₂ Cl₂

Oxidising Prop :

CaOCl₂ H₂S S CaCl₂ H₂O

CaOCl₂ 2FeSO₄ H₂SO₄ Fe₂(SO₄) ₃ CaCl₂ H₂O

CaOCl₂ KNO₂ CaCl₂ KNO₃

3CaOCl₂ 2NH₃ 3CaCl₂ 3H₂O N₂

CaOCl₂ 2KI 2HCl CaCl₂ 2KCl H₂O I₂

CaOCl₂ 2KI 2AcOH CaCl₂ 2KOAc H₂O I₂

CaOCl₂ Na₃AsO₃ Na₃AsO₄ CaCl₂

Reaction with acid :

CaOCl₂ 2HCl CaCl₂ H₂O Cl₂ ; Ca(OCl)Cl H₂SO₄ CaSO₄ H₂O C

Ca(OCl)Cl CO₂ CaCO₃ Cl₂

HXO₂ :

BaO₂ 2ClO₂ Ba(ClO₂)₂ O₂, Ba(ClO₂)₂ H₂SO₄ BaSO₄ HClO₂

(dil)

Only Known HClO₂. It is stable in alkaline solution but disproportionates in acid solution.

5HClO₂ 4ClO₂ HCl 2H₂O

HXO₃ : HClO₃ > HBrO₃ > HIO₃ are known and acidic order is as shown

Prepⁿ:

HClO₃ : Cl₂ 6NaOH 5NaCl NaClO₃ 3H₂O

Similarly electrolysis of hot halide solution with severe stirring gives the same product.

2Cl^- 2H₂O Cl₂ 2OH^- H₂

 

 

Cl₂ 6NaOH 5NaCl NaClO₃ 3H₂O

 

Properties :

* 3HClO₃ 2ClO₂ H₂O HClO₄

* IO₃^- 5I^- 6H 3I₂ 3H₂O

ClO₃^- 3SO₃^2- Cl^- 3SO₄^2-

Disproportionation : 4KClO₃ KCl 3KClO₄

2KClO₃ 2KCl 3O₂

HXO₄ : NaClO₃ H₂O NaClO₄ H₂

KClO₄ H₂SO₄ (conc.) HClO₄ KHSO₄

Electrode reaction

Props : K HClO₄ KClO₄(¯) H

Zn 2HClO₄ Zn(ClO₄)₂ H₂

Fe 2HClO₄ Fe(ClO₄)₂ H₂

Acidity order : HOX < HXO₂ < HXO₃ < HXO₄

Oxidising power : HOX > HXO₂ > HXO₃ > HXO₄

Thermal stability : HOX < HXO₂ < HXO₃ < HXO₄

 

OXIDES OF CHILORINE

1 4 6 7

Cl₂O ClO₂ Cl₂O₆ Cl₂O₇

(Brownish yellow) (Pale yelloow) (liq. - dark red colourless

solid - yellow) solid

Prepⁿ :

Cl₂ does not combine directly to produce its oxides but indirect methods are there.

Cl₂O : 2Cl₂ 2HgO(s) HgO. HgCl₂ Cl₂O (Brownish yellow gas)

^{dry in cooled tube Basic Hg(II) chloride} ¯

Condensed to oragne liq.

Props :

It dissolves in water : Cl₂O H₂O 2HClO

Explodes violently with NH₃.

3Cl₂O 10 NH₃ → 2N₂ 6NH₄Cl 3H₂O

It is oxidising agent

Cl₂O 2HCl 2Cl₂ H₂O

Structures :

ClO₂ : Prepⁿ :

3KClO₃ 3H₂SO₄ 3KHSO₄ HClO₄ 2ClO₂ H₂O

^{(powder) conc. Pale yellow gas}

2HClO₃ H₂C₂O₄ 2H₂O 2ClO₂ 2CO₂

2AgClO₃ Cl₂ 2AgCl 2ClO₂ O₂ [By this reaction pure ClO₂ obtained]

ClO₂ dissolves in water ClO₂ ClO O

producing dark green 2ClO H₂O HCl HClO₃

solution which decomposes

in presence of light.

but in alkali gives mixture of chlorite and chlorate.

2ClO₂ 2NaOH NaClO₂ H₂O

where 2ClO₂ 2NaOH H₂O₂ 2NaClO₂ O₂ 2H₂O

^{used in bleaching}

textiles and paper.

ClO₂ does not dimerise because odd e^—s undergoes delocalisation (in its own vaccant 3d-orbital)

Cl₂O₄ (Cl.ClO₄) is not the dimer of ClO₂. Actually it is Cl-perchlorate.

CsClO₄ ClOSO₂F Cs(SO₃)F ClOClO₃

Cl₂O₆ : Possible structures are :

liq dark red

Solid Yellow

Q. Prove that Cl₂O₆ is consisting ClO₂ and ClO₄^-

Prepⁿ : 2ClO₂ 2O₃ Cl₂O₆ 2O₂

Cl₂O₆ 2ClO₃ (monomer is paramagnetic)

Reactions : Cl₂O₆ H₂O HClO₃ HClO

Cl₂O₆ NaOH NaClO₃ NaClO₄ H₂O

Cl₂O₆ HF ClO₂F HClO₄

Cl₂O₆ NO₂ ClO₂ [NO₂] [ClO₄]^-

Cl₂O₇ (colourless solid) : It is the anhydride of HClO₄ and prepared from it by the action P₂O₅.

2HClO₄ P₂O₅ → 2HPO₃ Cl₂O₇

 

Structure :

INTER HALOGEN

Types : AX AX₃ AX₅ AX₇

ClF ClF₃ ClF₅ IF₇

BrF BrF₃ BrF₅

BrCl (lCl₃)₂ IF₅

ICl IF₃(unstable)

IBr

IF (unstable)

* 5IF IF₅ 2I₂ [The overall system gains B.E. by 250 kJ /mol]

* There are never more than two halogens in a moelcule.

* bonds are essentially covalent and b.p. increases as the E.N. difference increases.

* AX₅ & AX₇ type formed by large atoms like Br & I to accommodate mroe atoms around it.

* The interhalogens are genrally more reactive than the halogens (except F₂) due to weaker A-X bonds compared to X - X bond.

Reactions : ICl H₂O HCl HOI

BrF₅ 3H₂O HBrO₃ 5HF

IF₅ 3H₂O HBrO₃ 5HF

 

IF₇ H₂O IOF₅ 2HF (less)

4H₂O HIO₄ 7HF

(i) ClF is hightly reactive and as a fluorinating agent.

6ClF 2Al 2AlF₃ 3Cl₂

6ClF U UF₆ 3Cl₂

6ClF S SF₆ 3Cl₂

ClF SF₄ SF₅Cl

One pecularity with Cl :

In IInd case, the attacking species is I which has been supported by the formation of I in fuse state as follows :

3ICl [I₂Cl] [ICl₂]^-

* ICl₃ does not exist

but its dimer exist. 2ICl₃ I₂Cl₆

 

Structure is palnar.

I₂Cl₆ : liq. has appreciable electrical conductivity like other interhalogens.

I₂Cl₆ [ICl₂] [ICl₄]^-

BrF₃ [BrF₂] [BrF₄]^-

IF₅ [IF₄] [IF₆]^-

3ICl [I₂Cl] [ICl₂]^-

Polyhalides :

(i) Ki I₂ KI₃

(ii) ICl KCl K [ICl₂]^-

(iii) ICl₃ KCl K [ICl₄]^-

(iv) IF₅ CsF Cs [IF₆]^-

(v) ICl KBr K [BrICl]^-

Rb[ICl₂] RbCl ICl [not RbI Cl₂]

Here the products on heating depends on the lattice energy of the product halide. The lattice energy of alkali halide with smaller halogen is highest since the interatomic distance is least.

Structure of I₅^-, I^-₇, I₈^-2

in [N(CH₃)₄] I₇^- in Cs₂I₈

* Only F₃^- not known [due to absence of d-orbital] [i.e. Cs₂I₃ - I₂ - I₃]

I₃^-, Br₃^-, Cl₃^- are known Cl₃^- compounds are very less.

Stability order : I₃^- > Br₃^- > Cl₃^- : depends upon the donating ability of X^-.

PSEUDO HALOGEN

There are univalent ion consisting of two or more atoms of which at least one is N, that have property similar to those of the halide ions. E.g.

(i) Na-salts are soluble in water but Ag-salts are insoluble in water.

(ii) H-compounds are acids like HX.

(iii) some anions can be oxidised to give molecules X₂.

 

Anions : Acids Dimer

CN^- HCN (CN)₂

SCN^- HSCN(thiocyanic acid) (SCN)₂

SeCN^- (SeCN)₂

OCN^- HOCN (cyanic acid)

NCN^2-(Bivalent) H₂NCN(cyanamide)

ONC^- HONC (Fulminic acid)

N₃^- HN₃ (Hydrazoic acid)

CN shows maximum similarties with Cl^-, Br^-, I^-

(i) froms HCN

(ii) forms (CN)₂

(iii) AgCN, Pb(CN)₂, are insoluble

(iv) Inter pseudo halogen compounds ClCN, BrCN, ICN can be formed

(v) AgCN is insoluble in H₂O but soluble in NH₃

(vi) forms large no. of complex e.g. [Cu(CN)₄]^3- & [CuCl₄]^-3

[Co(CN)₆]^-3 & [CoCl₆]^-3

NOBLE GASES

* I.E. order : He > Ne > Ar > Kr > Xe > Rn

* M.P. order : He < Ne < Ar < Kr < Xe < Rn

* B.P. order : (-269ºC) same

* Atomic radius order : Same

* Density order : Same

* Relative abundance : Ar is highest (Ne, Kr, He, Rn)

"He" (helium) has the lowest b.p (-269ºC) of any liquid (lowest of any substance)

(i) It is used in cryoscopy to obtain the very low temperature required for superconductor and laser.

(ii) It is used in airships though H₂ is cheaper and has lower density compared to He because H is highly inflammable.

(iii) He is used in preference to N₂ to dil. O₂ in the gas cylinders used by divers. This is because N₂ is quite soluble in blood, so a sudden change in pressure causes degassing and gives bubbles of N₂ in the blood. This causes the painful condition called bends.

He is slightly soluble so the risk of bends is reduced.

* Noble gases are all able to diffuse through glass, rubber, plastics and some metals

* He liquid can exist in two forms . I-form when changes to II-form at l-point temperature many physical properties change abruptly.

e.g.

(i) Sp. heat changes by a factor of 10

(ii) Thermal conductivity increases by 10⁶ and it becomes 800 times faster than Cu

(iii) It shows zero resistance

(iv) It can flow up the sides of the vessel

 

* Ar, Kr, Xe can form clathrate compounds but He, Ne cannot due to their smaller size.

What is noble gas hydrate ?

e.g. Xe . 6H₂O formed only when

Ar . 6H₂O water freezes at high

Kr. 6H₂O pressure together with noble gas

===============================================================

Structure of Xenon Fluorides - The p-block Elements, CBSE, Class 12, Chemistry

Xenon Fluorides :-

(1) Xe F₂

(2) H₂ reduces Xe - fluorides to Xe

XeF₂ H₂ Xe 2HF and so on

(3) Xe - fluorides oxidise Cl^- to Cl₂ and I^- to I₂

XeF₂ 2HCl 2HF Xe Cl₂

XeF₄ 4KI 4KF Xe 2I₂

(4) Hydrolysis

XeF₂ reacts slowly with water

2XeF₂ 2H₂O 2Xe 4HF O₂

XeF₄ and XeF₆ react violently with water giving XeO₃

3XeF₄ 6H₂O 2Xe XeO₂ 12HF

XeF₆ 2H₂O XeO₃ 6HF

(explosive, white hygroscopic solid)

(5) SiO₂ also converts XeF₆ into XeOF₄

2XeF₆ SiO₂ SiF₄ 2XeOF₄

violet

Similary, XeO₃ XeOF₄ 2XeO₂F₂ , XeO₃ 2XeF₆ 3XeOF₄

(6) Xe - fluorides are also hydrolysed in alkaline medium.

2XeF₂ 4OH^- 2Xe 4F^- 2H₂O O₂

XeF₆ 7OH^- HXeO₄^- 3H₂O 6F^-

Xenate ion

2HXeO₄^- 2OH^- XeO₆^4-¯ Xe 2H₂O O₂

(7) They are used as fluorinating agent

2SF₄ XeF₄ 2SF₆ Xe

Pt XeF₄ PtF₄ Xe

(8) Act as a fluoride donor

XeF₂ MF₅ [XeF] [MF₆]^- (M = As, Sb, P)

XeF₆ BF₃ [XeF₅] [BF₄^-]

XeF₆ HF [XeF₅] [HF₂]^-

(9) Act as Flouride acceptor also :

XeF₆ RbF /CsF Rb /Cs [XeF₇]^-

2Cs [XeF₇]^- XeF₆ Cs₂[XeF₈]

XeF₄ MF M XeF₅^-

(alkali metals fluoride)