TyroCity: Chemistry 12 Notes

State Of A System, State Variables and State Function

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

State of a function (system) is a condition of existence which is described by some measurable properties. For e.g.: water exists in three different states i.e. solid, liquid & gas depending upon the temperature at 1atm pressure.
The measurable properties of gaseous system are pressure, temperature, volume, mass or composition of substances. Any change in these properties will change the state of a system and these properties are called state variables.
Some state variables depend only on the initial and final state but not the path or process how it is carried out, and they are called state function.
If water is heated from 0°C to 50°C, then we say that the change in temperature is 50°C regardless the process how water is heated.
Also, the vol. of 1 mole of any gas at NTP condition is 22.4 L regardless the process how that gas is prepared.

Depending upon the properties, there are two types of state variables:
Extensive variable
Those state variables that depend upon the quality of matter are called extensive variables. For e.g.: mass, moles, volume, internal energy, enthalpy, entropy and free energy.
Intensive variable
Those state variables that depend upon the property of matter are called intensive variables. For e.g.: temperature, density, refractive index, etc.

Rate Of Reaction And Stoichiometric Coefficient

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

Let’s consider a reaction

N2 + 3H2 → 2NH3

The rate of reaction can be expressed as,

Here, during disappearance of 1 mole of N, 3 mols of H2 are disappeared. So, the rate of disappearance of H2 is 3 times the rate of disappearance of N2.

The disappearance of 1 mole of N2 gives 2 moles of NH3. So the rate of formation of NH3 is 2 times the rate of disappearance.

The equivalent rate of reaction is,

Therefore, the equivalent rate of a reaction is obtained by dividing the rate of each species by its stoichiometric coefficient,

aA + bB → cC + dD

The equivalent rate of reaction is,

For the reaction,
H2 + I2 → 2HI

Express the rate of reaction in terms of all species for decomposition of N2O5. If the rate of formation of O2 is 2× 10-4 mol lit-1 S-1 calculate the rate of disappearance of N2O5 and rate of formation of N2.

Ferrous Sulphate Or Green Vitriol (FeSO4 7H2O)

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

Preparation:
It is obtained by dissolving Fe, FeO or FeCO3 in dil. H2SO4 the FeSO4 solution on crystallization gives light green crystals of FeSO4. 7H2O.
Fe + H2SO4 → FeSO4+H2
FeO + H2SO4 → FeSO4+H2O
FeCO3 + H2SO4 → FeSO4 + H2O + CO3
FeSO4 (aq) crystallization → FeSO4 7H2O
Green Uitrial

Properties:

1. It is light Green colored crystalline solid highly soluble in water.
2. It is an efflorescent compound and when exposed in air for long time is oxidized to give brown color of ferric salt.
4FeSO4 + O2 + 2H2O → 4Fe(OH)SO4
Basic Ferric Sulphate
(Brown in water)

3. Action of heat:
On heating, it gives anhydrous FeSO4 which is white in color.
FeSO4. 7H2O → FeSO4
Green White.
Anhydrous FeSO4 on Further heating decompose forming Fe2O3 Ferric oxide (brown)
2FeSO4 → Fe2O3 + SO2 + SO3
White Brown.

4. Action of nitric oxide:
FeSO4 solution absorbs nitric oxide forming a brown coloured complex of nitrosoferrous sulphate.
FeSO4 + NO → FeSO4NO
Nitroso Ferrous Sulphate (Ring test).

5. Action of potassium Ferrec cyanide:
With potassium fericyanide, it gives a deep blue coloured ppt of ferro ferricyanide commonly known as turn- bull’s ppt which is used for making blue coloured ink as blue pigment.
FeSO4 + K3 [Fe (CN) 6] → Fe3 [Fe(CN)6]2 + K2SO4
Ferroferricyanide
(Turn-bull’s ppt)

6. Hydrolysis:
It is soluble in water and gets hydrolyzed to give acidic salt solution as it is salt of strong acid and weak base.
FesSO4 + 2H2O → Fe (OH)2 +H2SO4
Weak base strong acid.

7. Reaction with K2Cr2O7 and KMno4 in acidic medium:
FeSO4 is a reducing agent and in acidic medium if reduce KMNo4 and K2 Cr2 O7
10 FeSO4 + 8H2SO4 + 2KMNO4 → 5Fe2 (SO4)3 + 2MNSO4+K2SO4+8H2O
Pink colorless

6. FeSO4 + 7H2SO4 + 2K2Cr2O7 → 3Fe2 (SO4)3 +Cr2 (SO4)3+ K2SO4+7H2O
Orange green

Uses:

It is used as reducing agent.
It is used in medicine.
It is used as modant in dye.
It is used in mfg of ink.

Manufacture Of Steel

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

By Bessemerisation process:
Principle:
In bessemerisation process, the impurities present in cast iron are removed by air oxidation and calculated amount of carbon is added in the form of spigelesien (Fe + Mn +C) is added to obtain Steel. The lining of Bessemer converter depends upon presence or absence of phosphorous. If phosphorous is present, then basic lining of CaO or MgO is used and if phosphorous is absent, then acidic lining of SiO2 is used. The reactions occurring during manufacture of steel are.

2C +O2 → 2CO
S + O2 → SO2
Si + O2 → SiO2
2Mn + O2 → 2Mno
MnO + SiO2 → MnSiO3
Manganous silicate (slag)

If phosphorous is present,

4P + 5O2 → 2P2O5
P2O5 + 3CaO → Ca3(PO4)2
Calcium phosphate (thomas slag)

Process:
Molten cast iron is kept in Bessemer converter lined internally by basic lining (if phosphorous is present) or acidic lining (if Phosphour is absent) and blast of air is passed into the mixture. At first impurities other than carbon are oxidized. Then carbon is oxidized to carbon monoxide which burns with light blue fame at the mouth of bessemer converter. When the flame dies out, calculated amount of spigelesin is added and mixed by passing air for some time. Then steel is manufactured. The process is completed in 15-20 minutes and the batch size is 500-600Kgs. The quality of steel obtained by Bessernerization process is not uniform. During the process some amount of Iron is lost as slag.

By Siemen Martin’s process or open hearth process:
Principle:

In open hearth process, the impurities present in cast iron are removed by oxidation by haematite. The percentage of carbon is decreased by adding scrap iron. The heat required for the process is obtained by burning per-heated producer gas (Co+N2) by regeneration of heat economy Depending upon the impurities the lining of hearth is acidic (If phosphorous is absent) or basic lining (if phosphorous is present). The percentage of carbon is maintained by adding required amount of splgelesien. The reactions during manufacture of steel are.

3C + 2Fe2O3 → 4Fe + 3CO2
3S + 2Fe2O3 → 4Fe + 3SO2
3Si + 2Fe2O3 → 4Fe + 3SiO2
SiO2 + Cao → CaSiO3

If phosphorous is present,

6P + 5Fe2O3 → 10Fe + 3P2O5
P2O5+3CaO → Ca3(PO4)2

Process:

Mixture of cast iron scrap iron , haematite and small amount of lime is kept on hearth of open hearth furnace & mixture is healed by burning producer gas by regenerative system. The outgoing hearth gas pre. Heats the incoming producer gas which an combustion can generate higher temperature. The slag formed is removed and a small amount of steel is withdrawn from the hearth and is analyzed. The percentage of carbon in steel can be increased by adding spigelicien and can be decreased by adding scrap iron. The process is slow and takes about 8-10 hours and quality steel is better as sample can be analyzed.

The advantages of open hearth process over bessemerization process are as follows:

The quality of steel is uniform.
Substance like Haematite, scrap iron is converted to valuable steel.
The loss of iron is very small.
The batch size in open hearth process is very large compared to bessernerisation process.

Copper Sulphate(CuSO4)

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

Copper Sulphate pentahydrate (CuSO4 5H2O) is commonly known as Blue Vitriol. It is obtained in lab by dissolving CuO, Cu(OH)2 or CuCO3 in dil H2SO4. The solution on crystallization gives blue triclinic crystals of CuSO4 5H2O.

CuO + H2SO4 → CuSO4 + H2O
Cu(OH)2 + H2SO4 → CuSO4 + H2O
CuCO3 + H2SO4 → CuSO4 + H2O + CO2
CuSO4 crystallization → CuSO4 5H2O
Blue Vitriol
In large scale, CuSO4 is obtained by reacting scrap copper with hot and dilute H2SO4 in presence of wir.
2Cu + 2H2SO4 + O2 → 2CuSO4 + H2O
Hot & dil

Properties

Hydrated copper sulphate is blue crystalline solid while anhydrous CuSO4 is white amorphous solid.
It is soluble in water.
Action of heat:
Blue vitriol on heating losses 4 molecules of water at 1000c to give monohydrate form and at 2300c to give anhydrous CuSO4.
CuSO4 5H2O 100 → CuSO4H2O 230 → CuSO4
Blue blueish white white

Anhydrous CuSO4 gives back blue vitrial in contact with water so anhydrous CuSO4 is used to detect water.
Anhydrous CuSO4 on further heating decompose forming CuO.
CuSO4 above 230 → CuO + SO3
Black

Action of water:

CuSO4 gives acidiec salt solution due to hydrolysis of Cu++ ion as it. Is salt of weak base and strong acid.
CuSO4 (aq) → Cu++ + SO4
Cu++ + 2H2O → Cu (OH)2 + 2H+

Reaction with KI:

KI reduces CuSO4 to cuprous iodide which appears as white ppt while KI is oxidized to I2

Reaction with NH3:

when NH3 is added to CuSO4 solution, a bluish white ppt of Cu(OH)2 is formed which dissolves in excess ammonia forming tetra amine copper (II) sulphate which is commonly known as Schweizer’s reagent.
CuSO4 + NH4OH → Cu(OH3)4SO4
Bluish white
CuSO4 + NH4OH + (NH4)2SO4 → [Cu(NH3)4]SO4 + 4H2O
Tetra amine copper (ii) sulphate (deep blue)

Uses

It is used as electrolyte in purification of copper & electroplating of Cu.
It is used in making schweizer’s reagent used for mfg of paper.
It is used as pesticide in controlling aphids and fungal growth.

Mohr’s Salt Or Ferrous Ammonium Sulphate FeSO4(NH4)2 SO4.6H2O)

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

Hydrated ferrous ammonium sulphate is commonly known as mohr’s salt .It is prepared by crystallization of equimolar solution of FeSO4 and (NH4)2SO4.

FeSO4(aq) + (NH4)2SO4 crystallization → FeSO4 (NH4)2SO4.6H2O.
Mohr’s salt
This double salt is more stable than FeSO4 alone and is used as reducing agent in redox fitration. During redox reaction Fe+2 ions mohr’s salt is oxidised to Fe+3 ions.

(Properties same as FeSO4. 7H2O)

First Law Of Thermodynamics

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

Total energy in the universe remains constant.
Energy can neither be created nor be destroyed but can be transferred from one form to another.
When Q amount of heat is supplied to the system, some part of it is used up to increase in its internal energy and remaining some part of it is used up for work done.

i.e. Q=∆E+W………………. (1)
If work is done by the system.
Q=∆E-W………………. (2)
If work is done on the system.
Where, Q= heat supplied
W=work done
∆E=change in internal energy.
∆E at constant volume
We have, from first law of thermodynamics;
Q=∆E+W
Q=∆E+P∆V
At constant volume, ∆V=0
So, Q=∆E
It means, at constant volume condition, the total amount of heat supplied is equal to change Internal energy of system.
∆E at adbiatic condition
We have, from first law of thermodynamics;
Q=∆E+W
At adbiatic condition, Q=0
So, -W=∆E
It means, at adbiatic condition, the work is done by utilizing the Internal energy of system.

Advantages of first law of thermodynamics

Total energy of the universe remains constant.
Different forms of energy are inter-convertible.
When one form of energy disappears, an equivalent amount of energy in another form appears.

Disadvantages of first law of thermodynamics

It doesn’t tell the extent and direction of the convertibility of one form of energy to another.
It doesn’t tell why chemical reactions do not proceed to completion.
It doesn’t tell why natural processes are unidirectional.
It doesn’t explain the feasibility and spontaneity of a process.
It says the equivalency of work and heat. But it has been observed that the work can be completely transformed into heat but heat cannot be transformed into work without permanent change in the system or surrounding which is not explained by the law.

Hess’s Law Of Constant Heat Summation

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

Hess’s law of constant heat summation states, “The total amount of heat involved in a physic-chemical process is same whether the process is done in single step or multiple steps involving intermediates.”

A can be converted to B into two ways:

Method I: A I directly converted to B

A = B + Q

Method II: A is first converted to C, then to D and finally to B

According to Hess’s Law,

Q = Q1 + Q2 + Q3

This law can be verified by taking the conversion of carbon to carbon dioxide.

Method I: Carbon is directly oxidized to carbon dioxide.

Method II: Carbon is first converted to carbon monoxide and then to carbon dioxide.

This result verifies Hess’s law of constant heat summation.

Application of Hess’s law:

This law can be used to determine heat of transition of allotropes.
This law can be used to determine heat of reaction of those reactions which cannot be performed in lab.

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.

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.

Mercury (Hg)

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

Symbol : Hg (a Lation, Hydrargyrum).

At. Number: 80

At. Mass: 200

Occurrence:-

Mercury occurs in nature in both free and combined state. The most common are of mercury is cinnabar (HgS).

Volumetric Analysis Formulae

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

This relation tells that the combining mass ratio of reactants is always in the ratio of their equivalent masses. This law is also termed as law of chemical equivalence.

Atomic mass = eqv. Mass x valency
G. eqv. / eqv. = Equivalent mass of substance expressed in grams is 1 g. eqv. Or 1 eqv.

Eqv. Mass of a compound.

Where basicity of acid is defined as the no. of H+ ions displaced or OH– ions combined per molecule of the acid.
eg. Eqv. Mass of H2SO4 = 98/2 = 49

Where acidity of the base is defined as the no. of H+ ions combined or OH– ions displaced per molecule of the base.
eg. Eqv. Mass of Ca(OH)2 = 74/2 = 37

eg. Eqv. Mass of Na2Co3 = 106/2 = 53

eg. Eqv. Mass of CO3— = 60/2 = 30
Eqv. Mass of Na+ = 23/1 = 23
In the case of acid, base and salt, the eqv. Mass can be obtained by the summation of positive and negative radical.