TyroCity: Chemistry 12 Notes

Cuprous Oxide Or Red Oxide Of Cupper (Cu2O)

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

It occurs in nature as cuprite. It is obtained by heating copper in air above 11000c.

4Cu+o2 above 11000c → 2Cu2o.

If can also be obtained by reducing alkaline Cuso4. (fehling’s solutional with reducing agents like glucose.

CuSO4+2NaOH → Cu(OH)2+Na2SO4
Cu(OH)2 → CuO+H2O
2CuO + C6H12O6 → Cu2O + C6H12O7

Properties

It is a red amorphous solid insoluble in water.
It dissolves in conc. HCl giving cuprous chloride.

Cu2O + 2Conc.HCl → Cu2Cl2 + H2O

It dissolves in conc. H2SO4 giving copper sulphate and metallic copper

Cu2O + H2OSO4 → CuSO4 + H2O + Cu

Uses

It is used in making ruby-red glass.
It is used in making anti-rust paints.
It is used in preparation of Cu2Cl2.

Transition Metals & Iron

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

The elements of ‘d’ block of periodic table including elements of Group IB to vii B. And viii are transition metals some important characteristics of transition metals are:

They have general configuration (n-1)d1-10 ns1-2 . They have partially filled valence shell and penultimate shell.
Transition metals have strong metallic bond, so they are heavy and herd. They have high mpt and bpt.
They are highly malleable and ductile they have high electrical and thermal conductivity.
They can absorb large quantity of the gases on their surface and this phenomenon is called occlusion. Because of this property these metals are used as catalyst in gaseous reaction.
Transition metals show variable oxidation state. For 3d, series, +2 is common O.S.

Eg. Sc → +2 and +3
Cu → +1 and +2
Mn → +2,+3,+4,+5,+6 and +7
MnSO4, Mn2O3, Mno2, Mn2o5, K2Mno4/HMno4

Transition metal forms colored compounds. The color of compounds is determined by number of unpaired electrons in d-orbital species with some no of unpaired electrons have same color.
Eg. V4 + → Cu4
(Ar)3d1 → (Ar)3d9 both have blue color.
1 Unpaired e+ 1 unpaired e–
They transition metal and metal ions show paramagnetic nature. The magnetic moment depends upon the number of unpaired electrons in d-orbital.
Transition metal ion can from complex with ligands. The central metal provides empty orbitals into which ligands donate tone pair of electrons forming co-ordinate co-Volant bond.

Half Life (t1/2)

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

Half Life of a reaction is time required to reduce the initial concentration to half. The half-life of a reaction depends on the order of reaction. The variation of half-life with order is given as:

Integrated rate law expression

For Zeroth order reaction

For first order reaction

Integrating on both sides, we get,

So, half-life of first order reaction is independent of initial concentration.

Numerical
The half-life of a first order reaction is 50 mins. Calculate the time required to complete 75% of the reaction.
Given,

Again,
initial concentration (a) = 100 (let) then
at time t,

Concentration left (a-x) = 100-75 = 25
We have,

Calculate the half period of first order reaction when rate constant is 5 year-1.
We have,
For 1st order reaction
t1/2 = 0.693/5
= 0.1386 year

Bond Energy Or Bond Enthalpy

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

Bond energy of a bond is amount of energy required to break 1 mole of a bond in gaseous state or energy released when one mole of a bond is formed in gaseous state.

In terms of bond energy,
Hreaction = Heat absorbed – Heat released = bond energies of reactants – bond energies of products

Estimate the enthalpy change for the reaction

Sol:
The amount of energy released during formation of 2moles of H-Cl bond = 2 × 430 = 860 KJ

H reaction = Energy absorbed – Energy released
= 618 – 860
= -182 KJ

Calculate the enthalpy change for the hydrogenation of ethane gas.

Given, bond energy of H -H bond = 435 KJ mole-1

Bond energy of C – H bond = 413 KJ mole-1

Bond energy of C -C bond = 347 KJ mole-1

Bond energy of C=C bond = 615 KJ mole-1

The amount of energy absorbed during reaction
= 413 × 4 + 615 + 435
= 2702 KJ

Energy released during reaction
= 6 × 413 + 347
= 2825 KJ

H reaction = 2825 – 2702 KJ = -123 KJ

Extraction Of Iron From Haematite

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

1. Concentration:
Haematite ore being oxide ore is concentrated by gravity separation process using hydraulic separator. The oxide is being heavier settles to the bottom while lighter impurities come to the surface and is removed.

2. Calcination:
The concentrated ore is heated in limited supply of air on the shallow hearth of Reverberatory furnace during calcination, flowing changes occur.

Moisture and volatile impurities are driven out.
Non-metallic impurities like s, p, etc are removed as their oxides.
S + O2 → SO2
P4 + 5O2 → 2P2O5
If any carbonate is present then it dissociates to give oxide.
FeCo3 → FeO + Co2

3. Smelting:
The calcined ore is mixed with lime stone (CaCO3) (Flux) and ore in the ratio of 8:1:4 and charged into blast furnace. The blast furnace is cylindrical steel vessel limed 6m in diameter. On passing Pre heated compressed air inside the furnace, four distinct zones are formed.

Zone of reduction combustion:
This zone lie at the bottom of the blast furnace where carbon burns in presence of pre heated air forming CO2 and heat.
C + O2 → Co2 + heat
Here, the temp is maintained above 15000c. This produces the energy required for the smelling of iron.

Zone of fusion:
This zone lies above zone of combustion. Here upcoming CO2 is reduced by red-hot coke to carbon monoxide. The reaction is endothermic and temp falls to 12000 -13000 c
Co2 + C → 2CO – heat
Red-hot
The spongy iron formed in zone of reduction melts here and any oxide escaped reduction is reduced here.
2Fe2O3 + 3C → 4Fe + 3CO2

Zone of slag formation:
This zone lies above zone of fusion and it has temp of about 10000c. In this zone calcium carbonate dissociate forming can (calcium oxide) which combines with silica (SlO2) present as impurity in Haematite forming calcium silicate (CaSiO3) as slag.
CaCo3 → CaO + CO2
CaO + SiO2 → CaSiO3
Calicum flicate (slag)
The slag is lighter than molten iron and to floats on the surface of the iron. The formation of prevents the oxidation of iron.

Zone of reduction:
This is the most important zone and has temperature of 600-7000c. In this zone Fe2O3 is reduced to iron by co in three steps.
3Fe2O3 + CO → 2Fe3O4 + CO2
Fe3O4 + CO → 3FeO + CO2
FeO + CO → Fe + CO2
(Solid state)
From the bottom of blast furnace, molten slag and molten iron are tapped out. This iron is impure and is called cast-iron or pig-iron.

Extraction Of Silver From Argentite

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

The chief are of silver is argentite and silver is extracted by hydrometallurgy process. The silver are is dissolved in cyanide solution to form soluble argento cyanide complex from which metal is obtained by reduction with more electropositive. The different steps involved in extraction of silver are:

1. Ore – Concentration:
Argentite being sulphide ore and is concentrated by froth flotation process. The pulverized ore is kept in large tank containing water and pine oil. The mixture is disturbed by passing compressed air where ore forms froth with pine oil & comes to the surface while impurities are left in water.

2. Treatment with sodium cyanide:
The concentrated are is treated with 0.4% to 0.7% aqueous solution of sodium cyanide and the current of air pass through it. The argentite ore dissolves in sodium cyanide forming sodium argento cyanide.
Ag2S + GNaCN → 2Na [Ag(CN)2] + NO2S
Sod argento cyanide
The reaction is reversible so is passed to oxidize Na2S to Na2SO4 such that the equilibrium shifts towards product.
Na2S + O2 → Na2SO4
The solution is filtered and the filtrate containing sodium argento cyanide is used to recover silver metal.

3. Precipitation of silver:

The solution obtained is treated with Zn scrap where Xn displaces silver from its complex.
Zn + 2Na [Ag (CN)2] → NO2[Zn (CN)4] | 2Ag
Sod Zincyanide
The ppt is collected, washed and fused to get compact mass of silver.

Refining:
The impure silver is purified by electrolytic method. A block of impure metal is anode while a thin strip of pure silver is cathode. A mixture of AgNO3 solution is electrolyte. On passing current impure silver dissolves and equivalent amount of pure silver is deposited at cathode.
AgNO3(aq) → Ag+ + NO–3
At cathode: Ag+ + e → Ag
At anode: Ag → Ag+ +e

Purity of Silver
The purity of silver is expressed in terms of fitness. Fitness of silver is mass of pure silver in grams present in every 1000 gram of silver sample. For eg. The fitness of silver in 900 means 900 gm of pure silver is present in 1000 gram of sample of silver.
In case of gold, purity is expressed in both fitness as well as carat. A 100% pure gold simple has purity of 24 carat. For eg. 18 carat gold is (18/24 × 100%) = 75% pure and has fitness 750.

Properties

It is a white lustrous metal having mpt 9600c and bpt 22120c.
It is sp gravity 10.5 and is highly malleable and ductile.
Silver is not affected by water, alkali and non-oxidising acids.
Action of HNO3
Silver dissolves in both dilute and conc. HNO3 having silver nitrate.
3Ag + 4HNO3 → 3AgNO3 + NO + 2H2O
Ag + ConC2HNO3 → AgNO3 + NO2 + H2O
Silver is readily attacked by sulphur and H2S to form a black stain of silver sulphide. (Ag2S)

Uses

Silver is used in making ornaments, coins, decorative articles etc.
Silver is used in electroplating of silver, making silver mirror etc.

Copper

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

Symbol: Cu (Cuprum)

At. No.: 29

At mass: 635

Electronic Configuration:

Occurrence
Copper occurs in both native state and combined state. The chief ores of copper are:

Laplace – Lavoiser Law Of Thermo Chemical Reaction

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

The amount of heat for the reverse of a reaction will be equal but will have opposite sign.

Order Of Reaction

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

Let’s consider a reaction,
A + B → product

The rate of reaction of above reaction is given by rate law expression,

Rate:

where k is constant called rate constant and is rate of reaction when concentration of all reactants is unit molarity (1m). Here m is order of reaction with respect to A, n is order of reaction w.r.t B and (m +n) is overall order of reaction. So, order of a reaction is the sum of the power to which the concentration of reactants is raised in the experimental rate law expression.

Unit of rate constant

Let’s consider a reaction,

A → product

The unit of rate constant depends upon the order of reaction.

For a reaction,

A → product

The rate law expression is,

when n = 0 The reaction is said to be a zeroth order reaction and for such reaction the rate of reaction is independent of concentration of reactant.

E.g.

Enzyme catalysed bio-chemical reaction.
Decomposition of HI on the surface of gold.
Reaction between H2 and Cl2 to give HCl in presence of light.

When, n =1,
The reaction is said to be a first order reaction and for such reaction the change rate is equal to the change in concentration of reactant.

Second Law Of Thermodynamics

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

The 2nd law of thermodynamics states, “All spontaneous process leads to the increase in entropy of the universe.”

In case of isolated system, the change in entropy of the system is the total entropy change. So, the process will be spontaneous when the entropy of a system increases.

In case of open system, the change in entropy of both system and surrounding is required. However, the system being very complex, the entropy change cannot be measured so, the entropy change of the system is only measured for open system. So, in terms of entropy change of system the criteria for spontancity is,

ΔS = +ve Spontaneous
ΔS = -ve non-spontaneous
ΔS = o equilibrium

However, there is some spontaneous process that occurs by decrease in entropy. Eg.

These examples show that entropy change alone is not an enough criteria for spontaneity. So, we need a thermodynamic function that encooperates both enthalpy and entropy.

Sign Convention Of Heat And Work

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

1. Heat (q)
Case I:
When heat is absorbed by the system, q = +ve.

Case II:
When heat is released by the system, q = -ve.

2. Work (w)
Case I: (Work of Expansion)
When work is done by the system, w = +ve.

Case II: (Work of Compression)
When work is done on the system, w = -ve.

Chemistry XII

Chemistry 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

General

Define Hydrogen Bond. How Is It originated?

General & Physical Chemistry (Section A)
Volumetric Analysis

Energetics of Chemical Reactions

Chemical Thermodynamics

Chemical Kinetics

Inorganic Chemistry (Section C)
Heavy Metals

Coinage Metal

Heavy Metals: Copper

Heavy Metals: Zinc

Heavy Metals: Mercury

Heavy Metals: Iron

Heavy Metals: Silver

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