A WARM WELCOME TO ALL THE STUDENTS IN THE ONLINE …

REACTION:

REACTION WITH BASES: Aluminium oxide also shows acidic nature, as it reacts with bases such as sodium hydroxide solution. By this reaction various aluminates are formed. Aluminates are compounds where the aluminium is found in the negative ion. This is possible because aluminiumhas the ability to form covalent bond with oxygen. With hot concentrated sodium hydroxide solution, aluminium oxide reacts to give a colorless solution of sodium tetrahydroxoaluminate.

Al2O3 +2NaOH +3H2O------2NaAl(OH)4

REACTIONS:

PHOSPHORUS(V)OXIDE:REACTION WITH WATER: Phosphorus (V) oxide reacts violently with water to give a solution containing a mixture of acids the nature of which depends on the conditions. Consider one of these phosphoric(v)acid, H3PO4 (also known as orthophosphoric acid).

P4O10 +6 H2O------4H3PO4 REACTION WITH BASE: Since H3PO4 is acidic so it reacts

with NaOH solution as follows: NaOH +H3PO4------NaH2PO4 +H2O

2NaOH + H3PO4------ Na2HPO4 +2H2O 3NaOH +H3PO4---------Na3PO4 +3H2O If phosphorous (V) oxide is reacted directly with sodium

hydroxide solution then same possible salts are obtained. 12NaOH + P4O10----4Na3PO4 +6H2O

REACTIONS:

THE SULPHUR OXIDES :(Sox)Two oxides are more important Sulphur dioxide and sulphurtrioxide.

SULPHUR DIOXIDE:REACTION WITH WATER:Sulphur dioxide is fairly soluble in water, reacting with it to give a solution of SULPHUROUS ACID,H2SO3

SO2 +H2O----- H2SO3 REACTION WITH BASE: Since it is acidic so it

reacts with NaOH and CaO to produce salts. SO2 +2NaOH----- Na2SO3 +H2O

Na2SO3 +H2O +SO2------2NaHSO3 CaO +SO2----- CaSO3

REACTIONS:

SULPHUR TRIOXIDE:SULPHUR TRIOXIDE REACTS VIOLENTLY WITH WATER TO PRODUCE A FOG OF SULPHURIC ACID DROPLETS.

SO3 +H2O-------- H2SO4 REACTION WITH BASE: SO3 REACTS WITH NaOH AQUEOUS SOLUTION TO GIVE

Na2SO4: 2NaOH +H2SO4--------- Na2SO4 +2H2O IN PRINCIPLE,SODIUM HYDROGENSULPHATE

(NaHSO4) CAN BE OBTAINED BY USING HALF MOLE OF SODIUM HYDROXIDE SO THAT ONLY ONE ACIDIC HYDROGEN OF H2SO4 IS USED.

SO3 CAN REACTS DIRECTLY WITH BASES TO FORM SULPHATES.e.g.IT WILL REACT WITH CALCIUM OXIDE TO FORM CALCIUM SULPHATE:CaO+SO3→CaSO4

REACTIONS:

THE CHLORINE OXIDES: (Cl2O3): CHLORINE FORMS TWO OXIDES,BUT TWO ARE

MORE IMPORTANT,CHLORINE(VII)OXIDE,Cl2O7 AND CHLORINE (I)OXIDE,Cl2O.

CHLORINE(VII)OXIDE IS ALSO KNOWN AS DICHLORINE HEPTAOXIDE AND CHLORINE (I)OXIDE AS CHLORINE MONOOXIDE.

CHLORINE(VII)OXIDE: CHLORINE(VII)OXIDE IS THE HIGHEST OXIDE OF

CHLORINE.IT MEANS THAT THE CHLORINE IN ITS MAXIMUM STATE OF +7.

IT HAS THE SAME TREND OF THE HIGHEST OXIDES OF THE PERIOD 3 ELEMENTS.THUS IT SHOWS TO BE VERY STRONGLY ACIDIC.

REACTIONS:

REACTION WITH WATER:

CHLORINE(VII)OXIDE REACTS WITH WATER TO GIVE THE VERY STRONG ACID,CHLORIC (VII) ACID.IT IS ALSO KNOWN AS PERCHLORIC ACID.

THE pH of typical solutions will be around 0 just like sulphuric acid.

Cl2O7 +H2O→2HC lO4.

REACTIONS:

REACTION WITH BASE: CHLORIC (VII) ACID REACTS WITH SODIUM

HYDROXIDE SOLUTION TO FORM A SOLUTION OF SODIUM CHLORATE (VII).NaOH +HClO4 →NaClO4 + H2O.

CHLORINE (VII)OXIDE ITSELF ALSO REACTS WITH SODIUM HYDROXIDE SOLUTION TO GIVE THE SAME PRODUCT.2NaOH +Cl2O7→2NaClO4 +H2O.

CHLORINE(I)OXIDE:REACTION WITH BASE: CHLORINE (I) OXIDE IS FAR LESS ACIDIC THAN CHLORINE (VII)OXIDE.IT REACTS WITH WATER TO SOME EXTENT TO GIVE CHLORIC (I)ACID, HOCl. IT IS ALSO KNOWN AS HYPOCHLOROUS ACID. Cl2O +H2O→2HOCl

REACTIONS:

REACTION WITH BASE:CHLORIC (I) ACID REACTS WITH SODIUM HYDROXIDE SOLUTION TO GIVE A SOLUTION OF SODIUM CHLORATE (I)(SODIUM HYPOCHLORITE).NaOH +HOCl →NaOCl+H2O

CHLORINE (I) OXIDE ALSO REACTS DIRECTLY WITH SODIUM HYDROXIDE TO GIVE THE SAME PRODUCT.2NaOH +Cl2O →2NaOCl +H2O

HOME-WORK:

Home work:

Do any one of the following:

How do acidic oxides reacts with water?

How do basic oxides reacts with water ?

How do acidic and basic oxides reacts with acids ?

HOW SO2 and SO3 reacts with water?

LECTURE NO:5

MESSAGE OF THE DAY:

W E A R E G O I N G T O S T A R T O U R O N L I N E C H E M I S T R Y L E S S O N T O D A Y . I H O P E Y O U A L L W I L L E N J O Y A N D L E A R N .

.

R U L E S O F T H E C L A S S :

1 ) B E O N T I M E F O R A L L Y O U R C L A S S E S .

2 ) R E S P E C T A L L P A R T I C I P A N T S O F T H E C L A S S .

3 ) D O N O T C R E A T E A N Y D I S T U R B A N C E .

4 ) R A I S E H A N D I F Y O U H A V E A Q U E S T I O N .

5 ) P A Y A T T E N T I O N T O Y O U R T E A C H E R .

A WARM WELCOME TO ALL THE STUDENTS IN THE ONLINE

CLASSES.THIS IS D.CHARLES

LESSON OBJECTIVES:

BY THE END OF THIS PART OF THE LESSON, STUDENTS WILL BE ABLE TO:

Recognise chlorides of period III ?

Differentiate between chlorides types of chlorides?

Why certain chlorides have high melting and boiling point?

Why certain chlorides conducts electricity while other donot ?

CHLORIDES OF PERIOD 3:

CHLORIDES OF THE PERIOD 3 ELEMENTS: STRUCTURE:

SODIUM CHLORIDE AND MAGNESIUM CHLORIDE ARE IONIC.THESE CONSISTS OF GIANT IONIC LATTICES AT A ROOM TEMPERATURE.

ALUMINIUM CHLORIDE AND PHOSPHORUS (V) CHLORIDE CHANGE THEIR STRUCTURE FROM IONIC TO COVALENT,WHEN THE SOLID TURNS TO LIQUID OR VAPOUR.

THE OTHER ARE SIMPLE COVALENT MOLECULES.

MELTING & BOILING POINT:

THE MELTING AND BOILING POINTS: SODIUM AND MAGNESIUM CHLORIDE ARE SOLIDS

WITH HIGH MELTING AND BOILING POINT.IT IS BECAUSE THEY HAVE STRONG IONIC ATTRACTIONS AND A LARGE AMOUNT OF HEAT IS NEEDED TO BREAK THEM.

THE REST ARE LIQUIDS OR LOW MELTING POINT SOLIDS EXCEPT ALUMINIUM CHLORIDE AND PHOSPHOROUS (V) CHLORIDE.IN THESE THE SITUATION IS QUITE COMPLICATED, THE ATTRACTION IN THE OTHERS WILL BE MUCH WEAK INTERMOLECULAR FORCES SUCH AS VANDERWAALS FORCES.THEY VARY DEPENDING UPON THE SHAPE AND SIZE OF MOLECULES,BUT WILL ALWAYS BE FAR WEAKER THAN IONIC BONDS.

MgCl2:

CONDUCTION:

IN THE ALUMINIUM CHLORIDE AND PHOSPHOROUS (V) CHLORIDE,THE SOLID DOES NOT CONDUCT ELECTRICITY,BECAUSE THE IONS ARE NOT FREE TO MOVE.IN LIQUID (WHERE IT EXISTS-BOTH OF THESE SUBLIMES AT ORDINARY AT ORINARY PRESSURE),THEY HAVE CONVERTED INTO A COVALENT FORM,AND SO DON’T CONDUCT EITHER.

CHLORIDES:

THE REST OF THE CHLORIDES DON’T CONDUCT ELECTRICITY EITHER IN SOLID OR MOLTEN BECAUSE THEY DON’T HAVE ANY IONIC OR ANY MOBILE ELECTRONS.

REACTIONS WITH WATER:

SODIUM AND MAGNESIUM CHLORIDE JUST DISSOLVE IN WATER.

THE OTHER CHLORIDES ALL REACTS WITH WATER IN DIFFERENT WAYS.

THE REACTION WITH WATER IS KNOWN AS HYDROLYSIS.

SiCl4:

Silicon tetrachloride is a colorless, fuming liquid with a pungent odor. It is decomposed by water to hydrochloric acid with evolution of heat. It is corrosive to metals and tissue in the presence of moisture. It is used in smoke screens, to make various silicon containing chemicals, and in chemical analysis.

PHYSICAL PROPERTIES OF MAGNESIUM CHLORIDE: IT IS AN IONIC COMPOUND,BUT WITH MORE

COMPLICATED ARRANGEMENT OF IONS,TO ALLOW FOR HAVING TWICE AS MANY CHLORIDE AS MAGNESIUM IONS.

AGAIN,LOT OF HEAT IS REQUIRED TO OVERCOME THE ATTRACTIONS BETWEEN THE IONS,AND SO MELTING AND BOILING POINT ARE HIGH.

SOLID MgCl2 IS A NON-CONDUCTOR OF ELECTRICITY BECAUSE THE IONS ARE NOT FREE TO MOVE.

HOWEVER,IT UNDERGO ELECTROLYSIS WHEN IONS BECOMES FREE ON MELTING.

MgCl2 DISSOLVES IN WATER TO GIVE A FAINTLY ACIDIC SOLUTION.(pH=6)

PHYSICAL PROPERTIES:

Physical Properties of AlCl3

Aluminium chloride has a very low melting and boiling point.

It sublimes at a temperature of 180°C. AlCl3 in a molten state is a poor conductor of electricity. The colour of aluminium chloride is white, but often it is

contaminated with iron trichloride, which makes it yellow in colour.

Aluminium chloride (AlCl3), also known as aluminiumtrichloride, is the main compound of aluminium and chlorine. It is white, but samples are often contaminated with iron(III) chloride giving it yellow color.The solid has low melting and boiling point.

SiCl4:

SILICON TETRACHLORIDE,(SiCl4) IT IS A SIMPLE COVALENT CHLORIDE.THERE

NOT ENOUGH ELECTRONEGATIVITY DIFFERENCE BETWEEN THE SILICON AND THE CHLORINE TO FORM IONIC BONDS.

IT IS A COLORLESS LIQUID AT ROOM TEMPERATURE,WHICH FUMES IN MOIST AIR.THE ONLY ATTRACTION BETWEEN THE MOLECULES ARE VAN DER WAAL’S DISPERSION FORCES.

IT DOES NOT CONDUCT ELECTRICITY BECAUSE OF LACK OF IONS OR MOBILE ELECTRON.

SiCl4:

IT FUMES IN MOIST AIR BECAUSE IT REACTS WITH WATER IN THE AIR TO PRODUCE HYDROGEN CHLORIDE.

IF WATER IS ADDED TO SILICON TETRACHLORIDE,THERE IS A VIOLENT REACTION TO PRODUCE SILICON DIOXIDE AND FUMES OF HCl.

IN A LARGE EXCESS OF WATER,THE SILICON TETRACHLORIDE WILL DISSOLVE TO GIVE A STRONGLY ACIDIC SOLUTION CONTAINING HCl.

SiCl4 +2H2O →SiO2 +4HCl

PCl3:

PHOSPHOROUS TRICHLORIDE:

THIS IS A SIMPLE COVALENT CHLORIDE.IT BECOMES A FUMING LIQUID AT ROOM TEMPERATURE.

IT IS A LIQUID BECAUSE THERE ARE VANDER DER WAAL’S DISPERSION FORCES AND DIPOLE-DIPOLE ATTRACTIONS BETWEEN THE MOLECULES.

IT DOES NOT CONDUCT ELECTRICITY BECAUSE OF LACK OF IONS OR MOBILE ELECTRONS.

PCl3 REACTS VIOLENTLY WITH WATER TO GIVE H3PO4 AND FUMES OF HYDROGEN CHLORIDE.

PCl3 +3H2O →H3PO4 +3HCl

PCl5:

PHOSPHOROUS PENTACHLORIDE: IT IS STRUCTURALLY MORE COMPLICATED.IT

IS A WHITE SOLID WHICH SUBLIMES AT 1630C.

THE HIGHER THE TEMPERATURE GOES ABOVE THAT,THE MORE THE PHOSPHOROUS (V)CHLORIDE DISSOCIATES TO GIVE PHOSPHOROUS (III)CHLORIDE AND CHLORINE.PCl5 ₌ PCl3 +Cl2

SOLID PHOSPHOROUS (V)CHLORIDE CONTAINS IONS SO,IT IS SOLID AT ROOM TEMPERATURE.THE FORMATION OF IONS INVOLVE TWO MOLECULES OF PCl5.

PCl5:

PCl5 HAS A VIOLENT REACTION WITH WATER PRODUCING FUMES OF HYDROGEN CHLORIDE.

THE REACTION OCCURS IN TWO STAGES,IN THE FIRST WITH COLD WATER,PHOSPHOROUS OXY CHLORIDE IS PRODUCED ALONG WITH HCl. PCl5

+H2O→POCl3 +2HCl IF THE WATER IS BOILING,PCl5 REACTS FURTHER

TO GIVE PHOSPHORIC (V) ACID AND HCl. PHOSPHORIC ACID IS ALSO KNOWN AS ORTHOPHOSPHORIC ACID. POCl3 +3H2O→H3PO4 +3HCl

THE OVERALL REACTION IN BOILING WATER IS JUST A COMBINATION OF THESE: PCl5+4H2O→H3PO4 +5 HCl

S2Cl2:

DISULPHUR DICHLORIDE:

IT IS FORMED WHEN CHLORINE REACTS WITH HOT SULPHUR

IT IS A SIMPLE COVALENT LIQUID (ORANGE & SMELLY).

THE SHAPE IS DIFFICULT TO DRAW,THE ATOMS ARE ALL JOINED UP IN A LINE BUT TWISTED.

SiCl4:

THE REASON FOR DRAWING THE SHAPE IS TO GIVE A HINT ABOUT WHAT SORT OF INTERMOLECULAR ATTRACTIONS ARE POSSIBLE.THERE IS NO PLANE OF SYMMETRY IN THE MOLECULES AND THAT MEANS THAT IT WILL HAVE AN OVERALL PERMANENT DIPOLE.

IT HAS VAN DER WAALS DISPERSION FORCES AND DIPOLE-DIPOLE ATTRACTIONS.

THERE ARE NO IONS IN DISULPHUR DICHLORIDE AND NO MOBILE ELECTRONS,SO IT NEVER CONDUCTS ELECTRICITY.

IT REACTS SLOWLY WITH WATER TO PRODUCE A COMPLEX MIXTURE OF THINGS INCLUDING HYDROCHLORIC ACID,SULPHUR,HYDROGEN SULPHIDE AND VARIOUS SULPHUR CONTAINING ACIDS AND ANIONS.

GROUP ALKALI METAL:

POINTS TO PONDER:

Why Li salts are covalent in nature while other are covalent in nature?

Give the trends of carbonates of alkali metals along the group ?

Why alkali metals are stored in kerosene/paraffin oil?

ALKALINE EARTH-METALS:

GROUP 2 ELEMENTS (ALKALINE EARTH –METALS)

PL GO THROUGH PAGES OF TEXT BOOK FROM 30-32(WE HAVE ALREADY DONE BEFORE.

TRENDS:

TRENDS IN REACTIVITY WITH WATER:THE GROUP 2 METALS BECOMES MORE REACTIVE TOWARDS WATER AS WE GO DOWN THE GROUP.FOR EXAMPLE.

BERRYLLIUM:IT HAS NO REACTION WITH WATER OR STEAM EVEN AT RED HOT.

MAGNESIUM:IT BURNS IN STEAM TO PRODUCE WHITE MAGNESIUM OXIDE AND HYDROGEN GAS. Mg +H2O →MgO +H2

REST OF THE REACTION GO TO PAGE NO.32 OF THE TEXT BOOK. CALCIUM, STRONTIUM AND BARIUM: THESE ALL REACTS WITH COLD WATER WITH INCREASING

VIGOUR TO GIVE METAL HYDROXIDES AND HYDROGEN. CALCIUM REACTS FAIRLY VIGOROUSLY WITH COLD WATER IN

AN EXOTHERMIC REACTION,BUBBLES OF HYDROGEN GAS ARE GIVEN OFF,AND A WHITE PRECIPITATE IS FORMED TOGETHER WITH AN ALKALINE SOLUTION.

M +2H2O →M (OH)2 +H2

REACTIONS:

REACTIONS OF GROUP 2 ELEMENTS WITH NITROGEN:ALL THESE ELEMENTS BURNS IN NITROGEN TO FORM NITRIDES,M3N2

3Ca +N2 →Ca3N2

THESE REACTS WITH WATER TO LIBERATE NH3

Ca3N2 +6H2O →3Ca(OH)2 +2NH3

Be3N2 IS VOLATILE WHILE OTHER NITRIDES ARE NOT SO.

TRENDS:

HOME-WORK:

Home work:

How do group II elements reacts with nitrogen and oxygen ?

Write about peculiar behaviour of beryllium?

Write about the trends of solubility of hydroxides and sulphates of group II ?

LECTURE NO:6

MESSAGE OF THE DAY:

W E A R E G O I N G T O S T A R T O U R O N L I N E C H E M I S T R Y L E S S O N T O D A Y . I H O P E Y O U A L L W I L L E N J O Y A N D L E A R N .

.

R U L E S O F T H E C L A S S :

1 ) B E O N T I M E F O R A L L Y O U R C L A S S E S .

2 ) R E S P E C T A L L P A R T I C I P A N T S O F T H E C L A S S .

3 ) D O N O T C R E A T E A N Y D I S T U R B A N C E .

4 ) R A I S E H A N D I F Y O U H A V E A Q U E S T I O N .

5 ) P A Y A T T E N T I O N T O Y O U R T E A C H E R .

A WARM WELCOME TO ALL THE STUDENTS IN THE ONLINE

CLASSES.THIS IS D.CHARLES

POINTS TO PONDER:

LESSON OBJECTIVES:

BY THE END OF THIS PART OF THE LESSON, STUDENTS WILL BE ABLE TO:

Recognise elements of group IV?

Why carbon shows oxidation state of IV and lead only II?

Why tetrahalides of carbon are not soluble in water?

Define inert pair effect? How it occurs?

Why melting and boiling point decreases not in regular pattern in group IV elements?

GROUP 4 ELEMENTS:

GROUP 4 ELEMENTS:THE GROUP ELEMENTS ARE: CARBON (C),SILICON (Si),GERMANIUM(Ge),TIN (Sn) AND LEAD (Pb).

MELTING AND BOILING POINTS: THE MELTING AND BOILING POINT GENERALLY

DECREASES DOWN THE GROUP.HOWEVER, THE DECREASE IS NOT REGULAR.

THE DECREASE IN MELTING AND BOILING POINTS SHOWS THAT INTER-ATOMIC FORCES ALSO DECREASE DOWN THE GROUP.THE MELTING AND BOILING POINT OF C AND Si ARE VERY HIGH.IT IS BECAUSE BOTH THESE ELEMENTS FORM GIANT MOLECULES.

THE MELTING POINT OF TIN IS LESS THAN LEAD.IT IS DUE TO FORMING A DISTORTED 1,2-CO-ORDINATED STRUCTURE RATHER THAN A PURE ONE.

STRUCTURE:

STRUCTURE OF THE ELEMENTS:THE FIRST TWO ELEMENTS C AND Si ARE CLEARLY NON-METALS.HOWEVER,THE ELECTRICAL PROPERTIES OF Si ARE LIKE THOSE OF SEMI-METALS (METALLOIDS).THE THIRD ELEMENT Ge IS PARTIALLY METAL AND NON-METAL.

THE LAST TWO ELEMENTS,Sn AND Pb ARE CLEARLY METALS.THUS THE METALLIC CHARACTER INCREASES DOWN THE GROUP IN GROUP 4 ELEMENTS.IT IS DUE TO DECREASE IN EFFECTIVE NUCLEAR CHARGE AND INCREASE IN NUMBER OF AVAILABLE (EMPTY)ORBITALS WITH INCREASE IN ATOMIC SIZE DOWN THE GROUP.

INERT PAIR EFFECT:

THE INERT PAIR EFFECT IN THE FORMATION OF IONIC BONDS:IF THE ELEMENTS IN GROUP 4FORMS +2 IONS,THEY WILL LOSE THE p ELECTRONS,LEAVING THE S2 PAIR UNUSED.FOR EXAMPLE, TO FORM A LEAD (II)ION,LEAD WILL LOSE THE TWO6p ELECTRONS,BUT THE 6s ELECTRONS WILL BE LEFT UN CHANGED-AN “INERT PAIR”.

You would normally expect ionization energies to fall as you go down a group as the electrons moves away from the Nucleus. That doesn’t happen in group 4.

The first chart shows how the total ionization energy needed to form 2+ ions varies as you go down the group. The values are all in KJmol-1 (check page 45)

Notice the slight increase between tin and lead. This means that it is slightly more difficult to remove the p

electrons from lead than from tin.

TIN &LEAD:

However, if you look at the pattern for the loss of all four electrons, the discrepancy between tin and lead is much more marked. The relatively large increase between tin and lead must be because the 6s2 pair is significantly more difficult to remove in lead than the corresponding 5s2pair in tin.

THEORY OF RELATIVITY:

THEORY OF RELATIVITY: With the heavier elements like lead, there is relativistic contraction of the orbitals, which tends to draw the electrons closer to the Nucleus than you would expect. Because they are closer to the Nucleus, they are difficult to remove .The heavier the element, the greater is this EFFECT.

This affects s electrons much more than p electrons. In the case of lead, the relativistic contraction makes it energetically more difficult to remove the 6s electrons than you might expect. The energy releasing terms when ions are formed(like lattice enthalpy or hydration enthalpy )are not enough to compensate for this extra energy. That means it doesn’t make energetic sense for lead to form 4+ ions.

INERT PAIR EFFECT:

THE INERT PAIR EFFECT IN THE FORMATION OF COVALENT BONDS: You need to think about why carbon normally forms four covalent bonds rather

than two. Using the electrons in boxes notation, the outer electronic structure looks like

this: (check page 45 of your text book). There are only two unpaired electrons. Before carbon forms bonds, though it

normally promotes one of the s electrons to the empty p orbitals. That leaves 4 unpaired electrons which (after hybridization) can go to form 4

covalent bonds. It is worth supplying the energy to promote the s electron, because the carbon can

then form twice as many covalent bonds. Each covalent bond that forms releases energy, and this is more than enough to supply the energy needed for the promotion.

Lead can do so, since the bond energies decreases as we go down the group. Bond energies tends to fall as atoms get bigger and the bonding pair is further from the two Nuclei and better screened from them.

For example, the energy released when two extra Pb-X bonds (where X is H or Clor whatever)are formed may no longer be enough to compensate for the extra energy needed to promote a 6s electron into the empty 6p orbital.

This would be made worse, of course, if the energy gap between the 6s and 6p orbital was increased by the relativistic contraction of the 6s orbital.