P Block Elements Notes | Group 15 | Chapter 7 | Chemistry |

P Block Elements Notes | Part I | Group 15 | Chapter 7 | Chemistry | CBSE |

P Block Elements Part 1

Group 15 

• The elements of Nitrogen family i.e. group 15 of the periodic table are: nitrogen (N), phosphorous (P), arsenic (As), antimony (Sb) and bismuth (Bi).
• Collectively, group 15 elements are called pnicogens and their compounds are called pniconides. (It means suffocation producing elements)

Symbol	Element	Atomic No	Electronic configuration	Group No	Period No
N	Nitrogen	7	[He] 2s2 2p3	15	2
P	Phosphorous	15	[Ne] 3s2 3p3	15	3
As	Arsenic	33	[Ar] 4s2 4p3	15	4
Sb	Antimony	51	[Kr] 4d10 5s2 5p3	15	5
Bi	Bismuth	83	[Xe] 4f14 5d10 6s2 6p3	15	6

• Nitrogen and Phosphorous are non metals
• Arsenic and Antimony are metalloids
• Bismuth is a moderate metal

Atomic  Properties 

Atomic size or Radii

a)The atomic and ionic radii of group 15 are smaller than corresponding elements of group 14 because on moving from left to right Z_eff increases as new electrons are added in same subshell and hence electrons are more strongly attracted towards the nucleus .                                                                                                                        

b) On moving down the group , ionic and covalent radii increases due to increase in number of shells .

Ionization Enthalpy 

The amount of energy which is required to remove an electron from isolated gaseous atom of an element .                                                                             

Factors affecting Ionization Enthalpy are as follows : 

I.E  ∝ Effective Nuclear Charge 

I.E ∝ 1 / Atomic size

I.E ∝ 1 / Shielding Effect 

Along Period : The I.E of group 15 are greater than group 14 because elements of group 15 has smaller atomic size than group 14 due to increase in effective nuclear charge along period .                                                       

Along Group : I.E of group 15 decreases down the group due to increase in number of shells . 

Electronegativity 

The tendency of atom of an element to attract the shared pair electron towards itself .                                       

Factors affecting Electronegativity are as follows :

Electronegativity ∝ Effective Nuclear Charge

Electronegativity ∝ 1 / Atomic size

Electronegativity of group 15 elements is higher than group 14 because group 15 elements have stable electronic configuration .                                                                                         

Electronegativity of group 15 decreases down the group due to increase in atomic size down the group.   

Physical Properties

Melting and Boiling Points 

Melting point increases from N to As and after that it starts to decrease because from N to As their melting point depends on magnitude of vanderwaal force.They form five covalent bond so melting point increases upto Arsenic . After , Arsenic the tendency of making 5 covalent bond decreases due to inert pair effect. So Sb and Bi form 3 covalent bonds instead of 5 . 

The boiling point increases regularly with increase in atomic number as we move down the group.

   Catenation (Self Linking Property)

Question : Nitrogen exist as diatomic gas and phosphorous exist as P₄. Why ?        

Answer : Nitrogen exist as diatomic gas because due to small size of nitrogen atom it has strong tendency to form p—p multiple bonding . Other element exist as octahedral molecule because they are not capable of forming p p multiple bonds as their atomic orbital are so large and diffuse that they cannot have effective overlapping.

Question : Why N₂ exist is less reactive at room temperature?

Answer : N₂ molecule contains N≡N  , this bond is very stable and require high bond dissociation enthalpy . So it is less reactive at room temperature .                                                     

Question : Why N₂ exist as gas while P , As and Sb exists as solid ?            

Answer : The N–N single bond is weaker than single P– P bond because of high inter-electronic repulsion of non-bonding electrons as a result of small bond length formed . So N₂ exist as gas and other exist as solid and due to this N₂ also show less catenation.

Metallic Character

The element of group 15 are less metallic than corresponding elements of group 14 due to increased effective nuclear charge and electronegativity of group 14 . However, on moving down the group , the metallic character increases because down the group electronegativity decreases. As a result valance electrons are lost more readily and hence the metallic character increases.

Chemical Properties 

Oxidation States 

Negative Oxidation State : 

• The tendency of formation of M ^3- of element decreases as we move down the group from N to Bi due to gradual decrease in their electronegativity and ionization enthalpy . 
• N and P accept three electrons and  form Nitride and Phosphide ion respectively while other elements do not form  since N and P have high Zeff and small size , so electron accepting tendency of three electron is high .
• Besides -3 , N and P also show -2 oxidation state in Hydrazine (NH₂NH₂) and diphosphine (P₂H₄) respectively. 

Positive Oxidation State :

• All the element of group 15 show positive oxidation state of +3 and +5.
• On moving down the group , stability of + 5 oxidation state decreases while that of +3 oxidation state increases due to inert pair effect.

Note : Nitrogen because of its small size , high electronegativity and tendency to form pπ —pπ multiple bonds , show all oxidation state from -3 to +5.

Maximum Covalency 

• Nitrogen show maximum covalency of 4 due to absence of d orbital in its valence shell.
• Phosphorous , Arsenixc and Antimony element have empty d orbital and can utilise all their orbital to exhibit covalency of 5 or 6 .
• Though , Bismuth has vacant d orbital yet it does not show covalency 5 due to inert pair effect . 

Disproportionation

• All the oxidation state of Nitrogen from +1 to +4 disproportionate in acidic medium.    

         3HNO₂ → HNO₃ + H₂O + 2NO

• Similarily , In Phosphorous nearly all oxidation state from -3 to +5 show disproportionation both in acidic and basic media . 

        4H₃PO₃ → 3H₃PO₄ + PH₃

Trends in Chemical Reactivity

Reactivity towards Hydrogen (Formation of Hydrides ) 

All elements of group 15 form volatile trihalides of formula EH₃ where E= N, P, As, Sb, Bi

NH₃ = Ammonia     PH₃ = Phosphine      AsH₃ = Arsine      SbH₃ = Stibine    BiH₃ = Bismuthine 

Preparation of Hydrides

By hydrolysis of binary metal compounds :

• Mg₃N₂ (Magnesium nitride) + 6H₂O → 3Mg(OH)₂ + 2NH₃ (Ammonia)
• Zn₃As₂ (Zinc arsenide) +6HCl → 3ZnCl₂ + 2AsH₃ (Arsine)
• Ca₃P₂ (calcium phosphide) + 6H₂O → 3Ca(OH)₂ + 2PH₃ (Phosphine)

By reduction of trichlorides :

ECl₃ +3LiAlH₄ → EH₃ + 3LiCl + 3 AlH₃ (E = N, P, As, Sb)

Structure

All the hydrides of group15 elements have pyramidal structure. All these elements undergo sp³ hybridization. 

Question : Why HNH angle in NH₃ is higher than HPH (PH₃) ?

Answer : Bond angle ∝ Electronegativity and size of central atom 

In NH₃ , N atom is more electronegative and has small size. Hence, it attracts bond pair towards it and these bond pair repel the lone pair and bond angle starts to increases. While from N →Bi , electronegativity decreases and size increases. Hence, bond angle decreases. 

Properties of Hydrides

Boiling points

The boiling points increases regularly as we move from PH₃ to BiH₃ since due to increase in molecular mass , van der waals force of attraction also increases resulting in increased boiling point. 

Question : Why boiling point of NH₃ is higher than PH₃ and AsH₃?

Answer: The abnormally high boiling point of NH3 is due to intermolecular hydrogen bonding. 

Question: Why NH₃ has less boiling point than SbH₃ and BiH₃?

Answer: This is because high van der waals force of attraction in SbH₃ and BiH₃ dominates over hydrogen bonding in NH₃.

The boiling point of hydrides of  group 15 elements follows the order:

PH₃ < AsH₃ < NH₃ < SbH₃ < BiH₃

Melting Points

Because of intermolecular H-Bonding, NH₃ has the highest melting point. 

Other hydrides of this group do not form H-Bonding and hence their melting point are lower than that of NH₃. 

Melting point increases regularly from PH₃ to SbH₃ due to increase in molecular mass, van der waals force of attraction also increases. 

The melting points of hydrides of group15 elements follows the sequence: PH₃ < AsH₃ < SbH₃ < NH₃

 Solubility

 NH₃ forms H-bonds with water while other hydrides do not. Therefore, NH₃ is soluble in H₂O while other hydrides are insoluble in H₂O.

Thermal Stability 

As we move down the group the size of the central atom increases and hence its tendency to form covalent bond with comparatively small H atom decreases. M—H bond strength also decreases and hence thermal stability also decreases as we move from NH3 to BiH3. 

Thermal stability of hydrides of group15 element decreases in the order:

NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃ 

Reducing Character

As we move from NH₃ to BiH₃, the thermal stability of hydrides decreases. Thus, their tendency to liberate hydrogen increases and hence reducing character increases from NH₃ to BiH₃. 

Reducing character of hydrides of group15 element increases in order:

NH₃ < PH₃ < AsH₃ < SbH₃ < BiH₃ 

Basic Nature

All the hydrides of group15 possess a lone pair of electron on the central atom and thus behave as Lewis base. 

Basic nature of hydrides of group15 follows the sequence : NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃ 

As the size of central atom increases, the lone pair of electron occupies a large volume. In other words, electron density on central atom decreases and consequently its tendency to donate a lone pair of electron decreases and hence basic strength decreases as we move from NH₃ to BiH₃. 

Reactivity towards Halogen (Formation of Halides)

A)Trihalides 

All elements of group15 form trihalides with general formula EX₃ 

Structure

Trihalides have pyramindal structure, i.e., central atom is sp³ hybridised. 

The bond angle of trihalides of group15 decreases in order: PF₃ < PCl₃ < PBr₃ < PI₃ 

This trend is due to reason that as electronegativity of halogen increases, the bond pair move away from the central P atom. As a result, bond pair – bond pair repulsion decreases and hence also bond angle also decreases. 

Properties

Question: Discuss the stability of trihalides of Nitrogen ?

Answer: NF₃ is only stable trihalide of nitrogen due to strong bond strength of N—F bond since both have comparatively small size. 

The instability of NCl₃, NBr₃, NI₃ is because of the weakness of N—X bond due to large size difference in size of N and X atom. 

Question: Why BiF₃ is predominantly ionic?

Answer: In BiF3 : F- →smaller anion → least polarisability 

Bi + → larger cation → least polarising power 

These both factors account for least covalent nature. So it is pre dominantly ionic. 

Question: Why trihalides of P, As and Sb behave as Lewis acids?

Answer : They accept a lone pair of electron due to presence of d orbital and thus behave as lewis acids. 

The Lewis acid strength decreases in order : PCl₃ > AsCl₃ > SbCl₃ and PF₃ > PCl₃ > PBr₃ > PI₃

Question: Why trihalides of Nitrogen behave as Lewis base?

Answer : They act as lewis base due to presence of lone pair and absence of d orbital. 

Question: Why NF₃ is not a Lewis base? 

Answer: NF₃ has a little tendency to donate a pair of electron because of the high electronegativity of F.

The lewis base strength of other trihalides increases as electronegativity of halogen decreases.

The Lewis base strength increases in order : NF₃ < NCl₃ < NBr₃ < NI₃ 

Question: Why Nitrogen triiodide ammoniate is stable only in the moist state?

Answer: This is because in dry state , it explodes with noise when struck liberating vapours of I₂. Thus, it is a mild and harmless explosive.    8NI₃.NH₃ → 5N₂ + 9I₂ + 6NH₄I

B)Pentahalides

P, As and Sb form pentahalides of the general formula EX5 due to presence of vacant d orbitain their respective valence shells. 

Question : Why N does not form pentahalides?

Answer: This is due to absence of d orbital in its valence shell. 

Question: Why pentahalides are thermally less stable than trihalides?

Answer : This is because of the following two reasons: 

• As we move down the group, stability of +3 oxidation state increases while that of +5 oxidation state decreases due to inert pair effect. 
• As the size of halogen increases from F to I, the strength of the phosphorous- halogen bond decreases and steric hindrance increases. 

Question: Why PCl₅ behave as good chlorinating agent?

Answer: As pentahalides are thermally less stable than the corresponding trihalides. Thus, PCl5 is decomposed and liberates Cl₂. Hence it acts as good chlorinating agent. 

PCl₅ → PCl₃ + Cl₂ 

Question: Why PF₅ does not undergo hydrolysis?

Answer: This is because P—F bond is stronger than P—O bond.

Question: Why pentachloride, pentabromide and pentaiodide of Bi does not exist?

Answer: This is probably due to the strongly oxidising properties of Bi⁵⁺ due to inert pair effect.

Question: Why all pentahalides behave as lewis acid?

Answer: All the pentahalides acts as lewis acid due to presence of vacant d orbital, the central atom can accept a pair of electrons thereby expanding its coordination number to 6, i.e., MX₅ + X^– → [MX₆]^– . As a result, the hybridization of the central atom changes from sp³d to sp³d².

Question: Why pentahalides are less covalent than trihalides?

Answer: In pentahalides, the oxidation state of central atom is high and thus its charge density and polarising power is also high. This results in greater covalent nature. 

Question: Bromides are more covalent than trihalides. Explain?

Answer: Size of bromide is greater than than chlorides. So it has more polarisability and hence it has more covalent nature. 

Question: Discuss the bond nature of pentahalides of P?

Answer: PCl₅ is covalent in vapour state but exist as [PCl₄]⁺[PCl6]^– in the crystalline state; the ions have tetrahedral and octahedral structure respectively. In the solid state PBr₅ exists as [PBr₄]⁺ Br^– while PI₅ exists as [PI₄]⁺ and I^– in solution. 

Reactivity towards Oxygen (Formation of Oxides)

Nitrogen has a strong tendency to form pπ—pπ multiple bond between Nitrogen and oxygen, whereas other elements of this group do not form.

Oxidation State of Element	Oxides of Nitrogen	Oxides of Phosphorous	Oxides of Arsenic	Oxides of Antimony	Oxides of Bismuth
+1	N2O Nitrous oxide	—	—	—	—
+2	NO Nitric oxide	—	—	—	—
+3	N2O3 Dinitrogen trioxide	P4O6 Phosphorous trioxide	As4O6 Arsenic trioxide	Sb4O6 Antimony trioxide	Bi2O3 Bismuth trioxide
+4	N2O4  Dinitrogen tetraoxide	P4O8 Phosphorous tetraoxide	—	—	—
+5	N2O5 Dinitrogen pentoxide	P4O10 Phosphorous pentoxide	As4O10 Arsenic pentoxide	Sb4O10 Antimony pentoxide	—

 Oxides of non metal are acidic, those of metalloids are amphoteric while that of metals are basic. Further, greater the electronegativity of the element , more acidic is the oxide. Among the oxides of the same element, higher the oxidation state of the element, more is its acidic strength. 

Acidic strength of oxides of nitrogen increases in the order: N₂O < NO < N₂O₃ < N₂O₄ < N₂O₅

Acidic strength of trioxides follows the order: N₂O₃  > P₄O₆ > As₄O₆ > Sb₄O₆

Acidic strength of pentoxides follows the order: N₂O₅  > P₄O₁₀ > As₄O₁₀ > Sb₄O₁₀         

Dinitrogen 

 Nitrogen exists as diatomic gas in the elemental state. Thus, it is called dinitrogen. 

Preparation  

By thermal decomposition of ammonium nitrite:  NH₄Cl + NaNO₂ → N₂ + 2H₂O + NaCl

By thermal decomposition of ammonium dichromate: (NH₄)₂Cr₂O₇ → N₂ +4H₂O + Cr₂O₃ 

By thermal decomposition of sodium or barium azide:

2NaN₃ (sodium azide) → 2Na + 3N₂               Ba(N₃)₂ (barium azide)→ Ba + 3N₂

Physical Properties

• Dinitrogen is a colourless, tasteless, non-toxic gas.
• It has two stable isotopes: ¹⁴N and ¹⁵N 
• It is very slighly soluble in water.
• It has low freezing (63.2K) and boiling point (77.2K). 
• It is adsorbed by activated charcoal. 

Question: Why is N₂ inert at room temperature?

Answer: N₂ contains a triple bond. This bond is very stable due to  high bond dissociation enthalpy. Thus, it is inert at room temperature. 

Chemical Properties

Action of active metal: Many active metal when heated at high temperatures, keep on burning in an atmosphere of dinitrogen forming their ionic nitrides.

6Li + N₂ → 2Li₃N (Lithium nitride)                         

2Al + N₂ → 2AlN (Aluminium nitride)

3Mg + N₂ → Mg₃N₂ (Magnesium nitride)             

 3Ca + N₂ → Ca₃N₂ (Calcium nitride)

Action of dihydrogen (Haber’s process) : When a mixture of dinitrogen and dihydrogen is heated at 700K under 200 atm, in presence of iron oxide as catalyst and molybdenum as promoter, ammonia is formed. 

N₂ + 3H₂ ↔ 2 NH₃ 

Question: What do you mean by active nitrogen? 

Answer: It is prepared by passing an electric spark through N₂ gas at low pressure. It forms active nitrogen and this process is associated with yellow- pink after glow. It is very reactive and reacts with no of elements and break many stable molecules. 

HC ≡ CH (Acetylene) + 2N (active nitrogen) → H≡C—C≡N (Cyanogen) +H₂

Ammonia

Preparation 

By heating ammonium salt with stronger base: 

(NH₄)₂SO₄ (ammonium sulphate) + 2NaOH → 2NH₃ + 2H₂O + Na₂SO₄

2NH₄Cl + Ca(OH)₂ (slaked lime) → 2NH₃ + 2H₂O + CaCl₂

NH₄Cl + KOH → NH₃ +H₂O +KCl

By the action of water on metal nitrides: 

Mg₃N₂ (magnesium nitride) +6H₂O → 3Mg(OH)₂ +2NH₃

AlN (aluminium nitride) + 3H₂O → Al(OH)₃ + NH₃

Physical Properties

• Ammonia is colourless gas with characteristics pungent smell called the ammonical smell.
• It is lighter than air and extremely soluble in water.
• When vapourised, liquid ammonia causes intense cooling. 

Structure

Nitrogen atom in ammonia is sp3 hybridised. NH₃ molecule has pyramidal geometry. 

Chemical Properties

It is highly soluble in water.   NH₃ + H₂O ↔ NH₄⁺ + OH^–

Question: How is NH₃ used to detect metals?

Answer: It forms complex compound with metals.

Cu²⁺ + 4NH₃ ↔  [Cu(NH₃)₄]²⁺ (deep blue colour)

Ag⁺ (colourless) + Cl^–  → AgCl (white ppt)        AgCl + 2NH₃ → [Ag (NH₃)₂]Cl (colourless)

Oxidation:

• 4NH₃ + 3Ca(OCl)₂ → 2N₂ + 3CaCl₂ +6H₂O
• 8 NH₃ +3Br₂ → N₂ + 6NH₄Br
• 4NH₃ +5O₂ → 4NO + 6H₂O

Nitric Acid

Preparation

In laboratory

NaNO₃ +H₂SO₄ → NaHSO₄ +HNO₃

On large scale it is prepared by Ostwald’s process

• 4NH₃ +5O₂ → 4NO + 6H₂O
• 2NO + O₂ → 2NO₂
• 3NO₂ + H₂O → 2HNO₃ + NO

Physical Properties

• It is colourless fuming liquid with pungent odour.
• Pure nitric acid freezes at 231.4K and boils at 355.6K
• It acquires a yellowish brown colour in presence of light.

Chemical Properties

Question : Why HNO₃ acts as strong oxidising agent?

Answer: It is a very strong oxidising agent since it readily gives nascent oxygen.  

2HNO₃(conc.) → H₂O + 2NO₂ + [O]

2HNO₃ (dil.) → H₂O + 2NO +3[O]

Question: Write some reactions which shows concentrated nitric oxide also oxidises non metal and their compounds? 

Answer :

I₂ +10HNO₃ → 2HIO₃ +10NO₂ +4H₂O

C + 4HNO₃ → CO₂ +2H₂O + 4NO₂

S₈ +48HNO₃ → 8H₂SO₄ + 48NO₂ +16H₂O

P₄ +20HNO₃ → 4H₃PO₄ +20NO₂ +4H₂O

Question : What do you mean by passivity of metals in HNO₃? 

Answer: When dipped in conc. HNO₃, metals like iron, chromium, nickel and aluminium loose their normal activity and become passive. The passivity of these metals is due to formation of thin protective layer of the metal oxide on surface of the metal which prevents further action. Example: 

3Fe + 8HNO₃ → FeO.Fe₂O₃ + 8NO₂ + 4H₂O

Question: Explain Ring test for nitrate ion?

Answer: The brown ring test depends upon the ability of Fe²⁺ ions to reduce nitrate ions to nitric oxide which then reacts with Fe²⁺ ions to form brown coloured complex. 

NO₃ +3Fe²⁺ +4H⁺ → NO + 3Fe²⁺ +2H₂O

[Fe(H₂O)₆]²⁺ + NO → [Fe (H₂O)₅ (NO)]²⁺ (brown) +H₂O

Allotropic Forms of Phosphorous

1)White or Yellow Phosphorous

Preparation :                             2Ca₃(PO₄)₂ + 6SiO₂ → 6CaSiO₃ +P₄O₁₀

                                                             P₄O₁₀ +10C → P₄ + 10CO

Properties:

• On exposure to light, white phosphorous turns yellow, therefore, it is called yellow phosphorous. 
• It is soft, translucent waxy white solid with garlic odour.
• It is very poisonous. Persons working with white phosphorous develop a disease known as Phossy jaw in which jaw bones decay.
• It is insoluble in water, but soluble in organic solvents such as CS₂ , alcohol and ether. 
• When it burns in air, it produces white fumes of phosphorous pentoxide  P₄ + 5O₂ → P₄O₁₀
• Because of its very low ignition temperature, it is always kept under water.
• It is very reactive and readily catches fire in air with a greenish glow which is visible in dark.

2)Red Phosphorous

Preparation: It is obtained by heating white phosphorous at 573K in an inert atmosphere for several hours. 

Properties: 

• It is hard crystalline odourless solid with iron grey lusture.
• It is non- poisonous in nature. 
• It is insoluble in water as well as in organic solvent.
• It is denser than white phosphorous and is a bad conductor of electricity.
• Being polymeric in nature, it is less reactive than white phosphorous.
• Its ignition temperature (543K) is much higher than that of white phosphorous (303K). Thus, it does not catch fire easily. 

3)Black Phosphorous

It has two forms : α-black phosphorous and β- black phosphorous.

Preparation:  α-Black phosphorous is formed when red phosphorous is heated in a sealed tube at 803K while  β- black phosphorous is prepared by heating white phosphorous at 473Kunder a sealed high pressure in an inert temperature. 

Properties:

• It is highly polymerized form of phosphorous and has black metallic lusture. 
• It has sharp melting point of 860K. 
• Like graphite, it is fairly good conductor of electricity.
• It is thermodynamically most stable allotrope of phosphorous and does not burn in air even upto 673K.  

Phosphine, PH₃ 

Preparation

From Metal Phosphide :         Ca₃P₂ (calcium phosphide) +6H₂O → 3Ca(OH)₂ + 2PH₃ ↑

Ca₃P₂ +6HCl → 3CaCl₂ +2PH₃↑

Laboratory method:       

 P₄ +3NaOH +3H₂O → 3NaH₂PO₂ (Sod. Hypophosphite) + PH₃ ↑

Structure

P in PH3 involves sp3 hybridisation. It has pyramidal structure.   

Physical Properties 

• It is colourless gas possessing unpleasant odour similar to that of rotten fish smell and is highly poisonous.
• It is slightly soluble in water. However , it is more soluble in organic solvents.
• It is little heavier than air.

Chemical Properties

Basic Nature: It is feebly basic and form salt with mineral acids under anhydrous conditions. 

PH₃ + HX → PH₄⁺X^– (Phosphonium halide)

Reaction through metallic salt solution : When it is bubbled through aqueous solution of copper and mercury salts, precipitates of corresponding phosphides are formed. 

3CuSO₄ +2PH₃  → Cu₃P₂ ↓ (Copper phosphide) + 3H₂SO₄

3HgCl₂ + 2PH₃ → Hg₃P₂ ↓ (Mercuric phosphide) + 6HCl

Decomposition : The solution of phosphine in water decomposes in presence of light giving red phosphorous and H₂.

4PH₃ → P₄ (Red phosphorous) + 6H₂ 

Phosphorous Halides

A) Phosphorous Trichloride

                              Preparation                                                 

 P₄ +6Cl₂ → 4PCl₃                      P₄ +8SOCl₂ → 4PCl₃ +4SO₂ +2S₂Cl₂

Physical Properties 

It is colourless pungent smelling liquid which boils at 347K and solidifies at 161K. It fumes in moist air. 

Chemical Properties

Action of water: It reacts violently with water to produce phosphorous acid and hypochloric acid.

PCl₃ + 3 H₂O → H₃PO₃ +3HCl

It acts as reducing agent: 

PCl₃ + SO₃ → POCl₃ + SO₂

PCl₃ + SO₂Cl₂ → PCl₅ + SO₂

Action of organic compounds

3CH₃CH₂COOH + PCl₃ → 3CH₃COCl + H₃PO₃

3C₂H₅OH + PCl₃ → 3C₂H₅Cl + H₃PO₃

B)Phosphorous Pentachloride

Preparation 

It is prepared by the reaction of white phosphorous with excess of dry chlorine or by action of dry chlorine on phosphorous trichloride. 

P₄ +10Cl₂ → 4PCl₅         PCl₃ +Cl₂ → PCl₅

Physical Properties 

It is a pale yellow  crystalline solid with characteristic pungent smell.  In solid state it exists as ionic solid  [PCl₄]⁺[PCl₆]^– in which the cation is tetrahedral while the anion is octahedral. 

Chemical Properties

Dissociation: When heated it sublimes but decomposes on stronger heating.   PCl₅ ↔ PCl₃ +Cl₂

Reaction with compound containing hydroxyl group: 

CH₃COOH (Acetic acid) + PCl₅ → CH₃COCl (Acetyl chloride) + POCl₃ + HCl

CH₃CH₂OH (Ethyl alcohol) + PCl₅ → CH₃CH₂Cl (Ethyl chloride) + POCl₃ + HCl

Oxoacids of Phosphorous

Structure of Oxoacids of Phosphorous 

 

# P Block Elements

# P Block Elements Notes

# P Block Elements Part 1

# P Block Elements Part 1 Notes

# P Block Elements Part 1 Solutions

 

Do share the post if you liked P Block Elements Notes. For more updates, keep logging on BrainyLads