B.B.S. VIDYA MANDIR, KADILPUR ALLAHABAD Assignment

SUBJECT – CHEMISTRY

P-BLOCK ELEMENTS

GROUP-15

N

P

As

Sb

Bi

Metallic Character increases

General Electronic Configuration = ns2np3

Atomic & Ionic radii from top to bottom increases. Ionisation enthalpy- from top to bottom decreases. Note: IE of gp-15 elements > gp -14 & gp-16, in gp-15 & gp-16 only Ist I.E is greater.

PHYSICAL PROPERTIES:

N2 is a diatomic gas, but all others are solid. Metallic character increases from top to bottom.

PHYSICAL PROPERTIES: Oxidation state :

(1) -3 oxidation state tendency decreases top to bottom & +5 increases (2) - N2 shows disproportionation-

Q. PCl5 is formed but NCl5 is not why?

Ans: Hybridisation of Pcl5= Sp3d, which means d-orbital is used. That’s NCl5 not possible due to non-availability of d-orbitals.

Reactivity towards Hydrogen:-

These elements react with H2 & from EH3. (E = Gp-15)

Stability of Hydrides decreases from top to bottom

Non-Metal

Metalloide

Metal

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Q. Why BiH3 has more reducing character than NH3,

Ans. The bond-dissociation energy of BiH3 is less than NH3

Bond angle decreases from top to bottom.

Highest – NH3

Basic character – top to bottom decreases.

Highest – NH3

Reactivity towards oxygen : E2O3 & E2O5 (E = Gp-15)

Reactivity towards Metal:

These elements react with metal to from binary compols.

Ex. - Ca3N2 - Calcium Nitride

Ca3P2 - Calcium Phosphide

Preparation of N2 :-

NH4Cl + NaNO2 N2 + 2H2O + NaCl (a)

Nitrogen is colourless, tasteless & odourless & non-toxic gas.

Nitrogen has two stable isotopes 7N14 & 7N15

N2 is inert at room temp due to high bond enthalpy of

React with metals & non-metals

3Mg + N2 Mg3N2

N2+ 3H2 Mg3N2

Uses:

To provide inert environment. An manufacturing of NH3. Liquid N2 is used as cryosurgery.

Preparation of NH3 :

NH2 – C –NH2 + 2H2O 2NH3( ) + H2O + CO2

(Pungent Smell)

(Urea)

Industrial Method : (Habber’s Process)

2NH3 (At high pressure and low temp.)

Catalyst – Fe or its oxide

Promotor – Mo (Molybedrum)

Pressure – 200atm. Temp – 700k

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2NH3(eq)

Properties :

NH3 is a colorless gas with Pungent smell. In solid & liquid state, it is associated through H-bonding. Shape – Trigonal Pyramidal. NH3 is highly soluble in water.

It acts as Lewis base, has I-lone pair of electron. NH3 is used for detection of metals. Ex-

Ag+ + Cl AgCl [Ag(NH3)2]Cl (aq) (white ppt) (Colourless)

NH3 is used for manufacture of fertilizers. Liquid NH3 is used as refrigerants.

Oxide of Nitrogen :

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500K

Pt, 9bar

+2

O

(dil)

(Conc)

Preparation of HNO3 : (Laboratory Method)

NaNO3 +H2SO4 NaHSO4 + HNO3

Industrial Method : (Ostwald’s Method)

Catalytic oxidation of NH3

4NH3 +5O2 NO + 6H2O

N2 + O2 NO2 (g)

3NO2 +H2O 2HNO3 + NO( )

Properties :

It is colourless Liquid. 68% of HNO3 used in Lab. It is a strong acid because it gives H3O+ ion in aq.soln

HNO3 + H2O NO3 + H3O+ Concentrated HNO3 is also used oxidizing agent. The product of oxidation depends upon the concentration of acid, temp & nature of material.

Cu + 8HNO3 3Cu(NO3)2 +2NO +4H2O

Cu + 4HNO3 Cu(NO3)2 +2NO2 +2H2O Note: Some metals like K, Cr don’t dissolve in conc HNO3 . bocz. Formation of a passive film of oxide on the surface.

Brown ring test :

Uses :

It is used for making T.N.T. It is used in pickling of steel.

Preparation of PCl3 :

Properties : As a chlorinating agent in organic compound.

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Ex.-

Hybridisation – SP3

Shape – Pyramidal.

Preparation of PCl5 :

In excess of Cl

P4 + 10Cl2 4PCl5

P4 + 10SOCl2 4PCl5 + 10SO2

Properties :

PCl5 + H2O POCl3 +2HCl

POCl3+ 3H2O H3PO4 + 3HCl (Excess water)

Hybridisation = SP3d Shape – Trigonal Pyramidal

On heating PCl5 . It decomposes as PCl3 + Cl2 It reacts with organic compds having OH groups & converts than in to chloro

compds.

Remark: In the Solid, it exists as an ionic compds as

Q. Is all 5 (P-Cl) bond’s equal?

Ans: P-Cl5 bonds are not equal. 2-axial P-Cl are longer than equatorial because in axis more

repulsion in the bond pair of e- . That’s why axial bonds are longer.

Oxoacids of Phosphorous

(i) H3PO3 – (Phosphorous Acid) Oxidation State +3

Structure:

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(ii) H3PO4 – (Phosphoric Acid) Oxidation State +5

Structure:

(iii) H4P2O5 – (Pyrophosphorous Acid) Oxidation State +3

Structure:

(iv) H4P2O7 – (Pyrophosphoric Acid) Oxidation State +5

Structure:

(v) H3PO2 – (Hypophosphorous Acid) Oxidation State +1

Structure:

Remark: Directly attached H-atoms show reducing nature/Power of acid.

GROUP-16

O S Se Te Po

Metallic Character increase down the gp.

Electronic Configuration = ns2np4

In atmosphere highest found element – Nitrogen On Earth’s Crust – Oxygen most abundant

H3PO2 > H3PO3

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S is found in form of Sulphide o& Sulphate. Gypsom CaSO4.2H2O Epsom Salt MgSO4.7H2O Cinebar - Hgs

Ionisation Enthalpy:

Q. Why the Ist I.E. of P & N > I.E of S or O

Ans: Ionisation enthalpy of P & N is greater than that of S or O as

P & N have half filled orbitals which are more stable.

Chemical Properties: Oxidation State -2 to +6

Oxide -

Peroxide-

Superoxide-

In fluorine compds .O2f2 = +1 , Of2 = +2,

Note : Due to small size & electrenegativity oxygen shows anomalous behaivour in gp-16.

Q. Why H2O is liquid & H2S is gas?

Ans: Due to electro negativity H2O shows H-bonding.

Note: SF6 is formed but Of6 not due to the non-availability of d-orbitals in O.

Reactivity with Hydrogen- H2E (E Gp-16)

H2O, H2S, H2Se, H2Te

Bond length increases from top to bottom. Bond dissociation increases. Acidic character increases from top to bottom. Thermal stability decreases from top to bottom.

Reactivity towards oxygen- (EO2 & EO3) (E- Gp-16)

Note :

[O] Nascent oxygen highly reactive as octet not formed. So given oxidation.

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Reactivity towards oxygen :-

Preparation of oxygen :

Heating oxygen containing salts

By thermal decomposition of oxides of Metal

Electrolysis of water: 2H2O 2H2 + O2

Properties:

It is colourless, odourless gas

3-stable isotopes- O2- directly reacts with nearly all metals & non-meatls.

Ex.-

Uses: for respiration & combustion - On the basis of nature acidic oxides which reacted H2O & give acid CO2+ H2O H2CO3

- Basic oxides reacte with H2O. give base MgO+ H2O Mg(OH)2

- Neupal- neither acidic nor basic

(CO, NO, N2O)

OZONE – (O3)

- At height of 20km (stratosphere) – it is formed from the oxygen in the presence of sunlight.

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- O3-layer protects us by filtering UV radiations.

Properties – Pure ozone is a light blue gas. Chages to dark blue when liquitied & violet-black when solidified.

Ozone is thermodynamically unstable. Ozone liberates oxygen as –

It acts as strong O.A

Super-sonic jets realeases the NO gas-which deplets the O3 layer NO + O3 NO2 + O2

SULPHUR- (S) – forms numerous allotrops.

Preparation of SO2 -

Properties :

Colourless gas, Pungent smell. Highly soluble in water.

Reacts with chlorine

When moist, SO2 act as R.A.

Ex- Uses: In manufacturing of H2SO4.

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OXO-ACIDS OF SULPHUR

(i) H2SO4 – (made buy contact process)

By contact process, 96%- 98% pure H2SO4 is obtained.

Properties:

Colorless, dense oily liquid. In aq.soln. it ionises in 2-step.

Dehydrating action of H2SO4 :

GROUP 17

F Cl

Gas Electronic Configuration – ns2np5

Br Liquid I At

Solid

Radioactive Element * Electron gain enthalpy – (∆egH) – Halogens have max. –ive e- gain enthalpy in corresponding

periods from top to bottom. ∆egH decreases { except F, Cl} F<Cl>Br>I & Cl>F>Br>I Remark:- In Periodic table highest (-)ive ∆egH chlorine Q Why the ∆egH of F is less than that of Cl? Ans Both F & Cl have 7e- in their outermost shell but due o the smaller size of F atom strong inter

electonic repulsion occurs which repels the incoming e-

Electrongativity;- Very high electongativity. It decreases form top to bottom.

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Highest electronegative element = F Bond length - increase Bond dissociation energy – decreasee . (Except – Cl) Q Enthalpy of dissociation of F2 is less than Cl2 Explain. Ans Relative large. e- - e- repulsion among the lone pair in F2 molecule, where they are much closer

to each other than Cl2. Chemical preperties;- (oxidation state - -1 to +7) F in every campd -1 (oxidation state) HClO, Cl +1, HClO2, Cl +3, HClO3, Cl + 5 Acid strength Increase. Reactivity Towards Hydrogen- H-F, H – Cl, H – Br, H - I (1) B.D.E decrease (2) Acidic Nature increase

Reactivity to-words oxygen:- Halogen form Many types of oxides OF2

F O2F2

* Cl, Br, I forms oxides in which the O.S of halogens varies from +1 to +7 Ex- +2 Cl2O, +4ClO2, +6Cl2 O6 - - - - - - - - - - - etc. Reactivity towords Metals- It React with metals to form metal hadides.. Mg + Br2 MgBr2

MF>MCl > MBr> MI (Ionic Bond) (M= Metal) Ionic Character = difference of electronegativity.

Remark:- NaF Halides in higher Oxidation state (More Ionic) MgF2 Will be more covalent than the lower Oxidation state. AlF3

More Covalent Reactivity of halogen towards another hologens to form a no of compounds known as inter

halogen compounds.

Type - ICl

Type – ICl3

Type - IF5, ICl5, BrF5, Brcl5

Type - IF 7

X – Large size halogen. = Small size halogen)

Note- X bond in inter halogen is weaker than xx bond in halogen (except F-F.)

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Preparation of Cl2

By – MnO2 + conc.HCl ∆ MnCl2 + Cl2 + 2 H2O. Commercial Method:- (Deacon’s Process) I By oxidation of HCl by atomospheric oxygen in presence of catalyst Cu2 cl2. at 723 K

2HCl +

H2O + Cl2 ( )

II By Electrolysis of brine [ Conc. NaCl Soln] Cl2 is liberated at anode.

2NaCl + 2H2O 2 NaOH + Cl2 (g) + H2 (g)

at anode at cathode Properities * Greenish Yellow gas with pungent & suffocating odour. * 2 – 5 times heavier than air * Cl React with a no. of metal & non metal. 2 Al + 3 Cl2 2 AlCl3

2 Na + Cl2 2 NaCl P4 + 6 Cl2 4PCl3

H2 + Cl2 2 HCl Reaction with NH3 NH3 in excess- 8 NH3 + 3Cl2 6NH4Cl + N2( ) Cl2 in cxcess- NH3 + Cl2 NCl3 + 3HCl (Explosive) * Cl act as strong oxidising agent. * it acts as bleaching action due to oxidation Process.. Cl2 + H2O 2HCl + [O] ( Nescent oxygen) * Coloured matter [O] Colourless matter. * Bleaching action of Cl is permanent, it blaeches vegetables or organic matter is presence of

moister (H2O) * CHCl3 Oxidation COCl2 (Phosgene Gas/Poisonous Gas) Imp. In the manufacturing of medicines CCl4. CHCl3 & DDT used. Preparation Of HCl:- * NaCl + H2SO4 420 K HCl + NaHSO4

* NaCl + NaHSO4 823 K HCl + Na2SO4 * HCl Gas can be derived by Conc. H2SO4

Properties:- * Colourless & Pungent Smelling gas * Extremly soluble in water & Ionises. HCl + H2O H3O+ + Cl-

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(g) (l) (aq) (aq) * A queous Soln of HCl is called Hydrochloric Acid. * It is a stong acid due to the high value of dissociation Constant. * It reacts with NH3 & gives white flame of NH4Cl * Aqua regia- Conc. HCl + Conc. HNO3 ( 3:1) * It is used for dissolving noble metals. Ex Au, Pt. * (1) Au + 4H+ +4 Cl- +

AuC + NO + H2O

* (2) 3 Pt + 16 H+ + 4N + 18 Cl- 3PtC

+ 4 NO + 8H2O OXO Acids with Halogen:-

GROUP 18 He 1S2 Exceptional no P orbital still in group. Ne Electronic Configunation – ns2 np6 (outer most shell) Ar These are gases & chemically unreactive Kr due to the complete duplet & octet Xe Rn (Radioactive element) * Xe & Rn are the rarest Element of this group. * Rn is obtained by decay process of Ra. (Radium)

Ionisation Enthalpy;- Very high I.E due to complet duplet & octet from top to bottom it

decreases. he has highest I.E in P.T Physical Properties:- All are monoatomic, atomicity = 1 * They are colourless, odourless & tasteless. * M.P & B.P is very less due to weak forces Chemical Prepeties:- Noble gases are least reactive in periodu table. These inertness is due to the following reasons. (1) Complete duplet & Octet.

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(2) High Ionisation Enthalpy.

* Xenon fluorides are colourless crystalline solid.

* They are powerful Morinating agent (Due to week bond)

* They are hydrolysed even in traces of water Molecules.

Partial hyorolysis of xet6 gives oxyfluoride

XeOF4 & XeO2 F2

Que. Is it xenon fluorides are hydrolysed. Redox as there is no change is O.S of Xe.

Ans. No Redox

XeO3 is colourless. Explosive solid has a Pyramidal molecular structure.

XeOF4- Colurless, volatile liquid has a square pyramidal structure.

Use-

* He – non inflammable light gas so used in filling ballons.

* Ne is used in discharged tubes & fluorescent.

* Ar is mainly used for inert atmosphere.

* Ar is used in filling electric bulbs.

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