Inorganic Finals

MEMORIZE THESE

What is environmental pollution?

•It is the effect of undesirable changes in our surroundings that have harmful effects on plants, animals and human beings.

What is pollutant?

A substance, which causes pollution, is known as pollutant

Physical state of pollutants

Pollutants can be solid, liquid or gaseous substances

Where are pollutants present in

greater concentration than in natural abundance

How are pollutants produced?

due to human activities or due to natural happenings.

Types of pollutants in air

Gaseous pollutants and particulate pollutants

Gaseous air pollutants

(a) Oxides of Sulphur
(b) Oxides of Nitrogen
(c) Hydrocarbons
(d) Oxides of Carbon (carbon dioxide, carbon monoxide)

Oxides of sulphurs are produced

when sulphur containing fossil fuel is burnt

What is the most common species of oxide of sulphur?

sulphur dioxide, is a gas that is poisonous to both animals and plants

Harmful effects of oxides of sulphur

-respiratory disease (asthma, bronchitis, emphysema)
-irritation to the eye
-stiffness of flower buds

Main constituent of air

Nitrogen and Oxygen

When to nitrogens react with oxygens?

•At high altitudes when lightning strikes, they combine to form oxides of nitrogen.
•NO2 is oxidised to nitrate ion, NO3− which is washed into soil, where it serves as a fertilizer.
In an automobile engine, (at high temperature) when fossil fuel is burnt, nitrogen and oxygen combine to yield significant quantities of nitric oxide (NO) and nitrogen dioxide ( NO2 )

Harmful effects of nitrogen

-damage the leaves and retard the rate of photosynthesis
-lung irritant
-toxic to living tissues
-harmful to various textile fibers and metals

What are hydrocarbons composed of?

hydrogen and carbon only

How are hydrocarbons formed?

by incomplete combustion of fuel used in automobiles.

Harmful effects of hydrocarbons

•Hydrocarbons are carcinogenic, i.e., they cause cancer.
•They harm plants by causing ageing, breakdown of tissues and shedding of leaves, flowers and twigs.

Oxides of carbon

CO and CO2

What is carbon monoxide and why is it harmful

It is a colourless and odourless gas, highly poisonous to living beings because of its ability to block the delivery of oxygen to the organs and tissues.

How is CO produced?

It is produced as a result of incomplete combustion of carbon

How is CO mainly released?

•Carbon monoxide is mainly released into the air by automobile exhaust.

What are the other sources of CO?

•Other sources, which produce CO, involve incomplete combustion of coal, firewood, petrol, etc.

Harmful effects of CO

•It binds to haemoglobin to form carboxyhaemoglobin, which is about 300 times more stable than the oxygen-haemoglobin complex.
•In blood, when the concentration of carboxyhaemoglobin reaches about 3-4 percent, the oxygen carrying capacity of blood is greatly reduced.
•This oxygen deficiency, results into headache, weak eyesight, nervousness and cardiovascular disorder.
•This is the reason why people are advised not to smoke.
•In pregnant women who have the habit of smoking the increased CO level in blood may induce premature birth, spontaneous abortions and deformed babies.

How is CO2 released?

•Carbon dioxide (CO2) is released into the atmosphere by respiration, burning of fossil fuels for energy, and by decomposition of limestone during the manufacture of cement.
•It is also emitted during volcanic eruptions.

Where is CO2 confined?

to troposphere only

What does increased use of fossil fuels do?

•With the increased use of fossil fuels, a large amount of carbon dioxide gets released into the atmosphere. Excess of CO2 in the air is removed by green plants and this maintains an appropriate level of CO2 in the atmosphere.

How does global warming occur?

•About 75 % of the solar energy reaching the earth is absorbed by the earth's surface, which increases its temperature.
•The rest of the heat radiates back to the atmosphere.
•Some of the heat is trapped by gases such as carbon dioxide, methane, ozone, chlorofluorocarbon compounds (CFCs) and water vapour in the atmosphere
•Thus, they add to the heating of the atmosphere.
•This effects is called the greenhouse effect and it causes global warming.
•Carbon dioxide is the major contributor to global warming.

Effects of global warming

•The average global temperature will increase to a level which may lead to melting of polar ice caps and flooding of low lying areas all over the earth.
•Increase in the global temperature increases the incidence of infectious diseases like dengue, malaria, yellow fever, sleeping sickness etc.

Why is pH of rain slightly acidic?

normally rain water has a pH of 5.6 due to the presence of H+ ions formed by the reaction of rain water with carbon dioxide present in the atmosphere.

What is acid rain?

•When the pH of the rain water drops below 5.6, it is called acid rain.
•Acid rain refers to the ways in which acid from the atmosphere is deposited on the earth's surface.

Causes of acid rain

•Acid rain is a byproduct of a variety of human activities that emit the oxides of sulphur and nitrogen in the atmosphere.
•Burning of fossil fuels (which contain sulphur and nitrogenous matter) such as coal and oil in power stations and furnaces or petrol and diesel in motor engines produce sulphur dioxide and nitrogen oxides.
•SO2 and NO2 after oxidation and reaction with water are major contributors to acid rain, because polluted air usually contains particulate matter that catalyse the oxidation.

Harmful effects of acid rain

•Acid rain is harmful for agriculture, trees and plants as it dissolves and washes away nutrients needed for their growth.
•It causes respiratory ailments in human beings and animals.
•When acid rain falls and flows as ground water to reach rivers, lakes etc. it affects plants and animal life in aquatic ecosystem.
•It corrodes water pipes resulting in the leaching of heavy metals such as iron, lead and copper into the drinking water.
•Acid rain damages buildings and other structures made of stone or metal.
•The Taj Mahal in India has been affected by acid rain.

What are particulate pollutants

•Particulates pollutants are the minute solid particles or liquid droplets in air.

where are particulate pollutants present in?

•These are present in vehicle emissions, smoke particles from fires, dust particles and ash from industries etc.

What is smog derived from? What is the most common example of it?

•The word smog is derived from smoke and fog.
•This is the most common example of air pollution that occurs in many cities throughout the world.

Types of smog

two types
Classical smog and photochemical smog

Where does classical smog occur?

cool humid climate

what is classical smog mixture of?

smoke, fog and sulphur dioxide

What is the another name of classical smog and why?

Chemically it is a reducing mixture and so it is also called as reducing smog

Where does photochemical smog occur?

in warm, dry and sunny climate

The main components of photochemical smog result form?

the action of sunlight on unsaturated hydrocarbons and nitrogen oxides produced by automobiles and factories.

Why is photochemical smog called oxidizing smog?

Photochemical smog has high concentration of oxidizing agents such as NO2 and O3, and is, therefore, called as oxidizing smog.

Formation of photochemical smog

•When fossil fuels are burnt, a variety of pollutants are emitted into the earth's troposphere.
•Two of the pollutants that are emitted are hydrocarbons (unburnt fuels) and nitric oxide (NO).
• When these pollutants build up to sufficiently high levels, a chain reaction occurs from their interaction with sunlight in which NO is converted into nitrogen dioxide (NO2).
•This NO2 in turn absorbs energy from sunlight and breaks up into nitric oxide and free oxygen atom
•Oxygen atoms are very reactive and combine with the O2 in air to produce ozone.
•The ozone formed in the above reaction (ii) reacts rapidly with the NO(g) formed in the reaction (i) to regenerate NO2 . NO2 is a brown gas and at sufficiently high levels can contribute to haze.
•Ozone is a toxic gas and both NO2 and O3 are strong oxidizing agents and can react with the unburnt hydrocarbons in the polluted air to produce chemicals such as formaldehyde, acrolein and peroxyacetyl nitrate (PAN).

Primary photochemical smog

N2/O3

Secondary photochemical smog

Formaldehyde, Acrolein, PAN

Effects of photochemical smog

The common components of photochemical smog are ozone, nitric oxide, acrolein, formaldehyde and peroxyacetyl nitrate (PAN). It causes serious health problems. They may include-
•Both ozone and PAN act as powerful eye irritants.
•Ozone and nitric oxide irritate the nose and throat and their high concentration causes headache, chest pain, dryness of the throat, cough and difficulty in breathing.
•Photochemical smog leads to cracking of rubber and extensive damage to plant life.
•It also causes corrosion of metals, stones, building materials, rubber and painted surfaces.

How can photochemical smog be controlled?

•If we control the primary precursors of photochemical smog, such as NO2 and hydrocarbons, the secondary precursors such as ozone and PAN, the photochemical smog will automatically be reduced.
•Usually, catalytic converters are used in the automobiles, which prevent the release of nitrogen oxide and hydrocarbons to the atmosphere.
•Certain plants e.g., Pinus, Juniparus, Quercus, Pyrus and Vitis can metabolize nitrogen oxide and therefore, their plantation could help in this matter.

Water pollutants

Microorganism-domestic sewage
organic wastes-domestic sewage, animal excreta and waste, decaying animals and plants, discharge from food processing factories
plant nutrients-chemical fertilizers
Toxic heavy metals-industries and chemical factories
Sediments-erosion of soil by agriculture and strip mining
Pesticides-chemicals used for fungi and wastes
Radioactive substances-mining of uranium containing materials
heat- water used for cooling in industries

Soil pollutants

pesticides and herbicides

Pesticides

•Pesticides are basically synthetic toxic chemicals with ecological repercussions.
•The repeated use of the same or similar pesticides give rise to pests that are resistant to that group of pesticides thus making the pesticides ineffective.
•Therefore, as insect resistance of DDT (a pesticide) increased, other organic toxins such as Aldrin and Dieldrin were introduced in the market by pesticide industry.
•Most of the organic toxins are water insoluble and nonbiodegradable.
•These high persistent toxins are, therefore, transferred from lower trophic level to higher trophic level through food chain.
•Over the time, the concentration of toxins in higher animals reach a level which causes serious metabolic and physiological disorders

Herbicides

•Most herbicides are toxic to mammals but are not as persistent as organo-chlorides / pesticides.
•These chemicals decompose in a few months.
•Like organo-chlorides, these too become concentrated in the food web.
•Some herbicides cause birth defects.
•Studies show that corn fields sprayed with herbicides are more prone to insect attack and plant disease than fields that are weeded manually.
Pesticides and herbicides represent only a very small portion of widespread chemical pollution. A large number of other compounds that are used regularly in chemical and industrial processes for manufacturing activities are finally released in the atmosphere in one or other form.

What is green chemistry?

Green chemistry is the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products

Twelve principles of green chemistry

Waste prevention
Atom economy
Safer syntheses
Safer products
Safer auxiliaries
Energy efficiency
Renewable feedstocks
Derivative reduction
Catalysis
Degradability
Pollution prevention
Accident prevention

Explain waste prevention

It is advisable to avoid creating waste than to clean it after it is formed as per the adage "prevention is better than cure". The process in which only target product with minimum or no by product/waste are synthesized, are utilized. Treating and disposing the waste safely is expensive and as a result, the production cost increases.

Explain atom economy

The synthetic processes giving maximum product yield should be adopted. These should be designed in such a way that all the reactants are incorporated into the final products.

Explain safer synthesis

The synthetic processes should be designed so as to minimize or prevent the production of hazardous substances. To safeguard the workers handling toxic chemicals, respirators, gloves and other appropriate protective clothing are used. However, such ventures are not economical. In such cases, green synthesis needs to be adopted that follows alternative reactions to minimize their toxicity.

Explain safer products

The chemical products should be designed to preserve efficacy of function while reducing toxicity. It is envisaged to produce the chemical products specially those being used in cosmetics, pharmaceuticals, etc., that will not have any side effects on the people using it and on the environment

Explain safer auxiliaries

The chemical synthesis is assisted by solvent medium. It is recommended to use alternative solvents and other auxiliaries which are greener in nature such as aqueous medium, liquid carbon dioxide, ionic liquids and solvent free systems

Accepted solvent

Methanol

Green solvents

ethanol, water

Not accepted solvents

Methylene chloride
chloroform
perchloroethylene
carbon tetra chloride
CFC
benzene
hexane

Explain energy efficiency

Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic reactions should be conducted at ambient temperature and pressure. The chemical processes are to be designed in such a way that they are less energy intensive, that is, reactions occur at mild conditions and require less time to complete. Such reactions needs minimum energy for product formation.

Green Chemistry Application

(i) Dry Cleaning of Clothes
(ii) Bleaching of Paper
(iii) Synthesis of Chemicals
(iv) 'Green Solution' to Clean Turbid Water

Explain dry cleaning of clothes

•Tetra chlroroethene (Cl2C=CCl2 ) was earlier used as solvent for dry cleaning.
•The compound contaminates the ground water and is also a suspected carcinogen.
•The process using this compound is now being replaced by a process, where liquefied carbon dioxide, with a suitable detergent is used.
•Replacement of halogenated solvent by liquid CO2 will result in less harm to ground water.
These days hydrogen peroxide (H2O2 ) is used for the purpose of bleaching clothes in the process of laundry, which gives better results and makes use of lesser amount of water.

Explain bleaching of paper

•Chlorine gas was used earlier for bleaching paper.
•These days, hydrogen peroxide (H2O2 ) with suitable catalyst, which promotes the bleaching action of hydrogen peroxide, is used.

Explain synthesis of chemicals

Ethanal (CH3CHO) is now commercially prepared by one step oxidation of ethene in the presence of ionic catalyst in aqueous medium with a yield of 90%.

Explain 'Green Solution' to Clean Turbid Water

•Powder of kernel of tamarind seeds has been found to be an effective material to make municipal and industrial waste water clean.
•It is non-toxic, biodegradable and cost-effective material.
•This powder is usually discarded as agricultural waste.
•The present practice is to use alum to treat such water.
•It has been found that alum increases toxic ions in treated water and can cause diseases.

Reasons of Naming Alkaline Earth Metals

The oxides of the three metals (Ca, Sr and Ba) were known much earlier than the metals themselves and were called alkaline earths, since they were alkaline in character and occurred in nature as earths [lime (CaO), strontia (SrO), baryta (BaO)]. Therefore, when Ca, Sr and Ba were discovered , they were named alkaline earth metals.

Physical Properties of alkaline earth metals

1. Physical state
2. Melting and boiling points
3. Atomic volume, atomic and ionic radii
4. Ionization energy
5. Electropositive character
5. Electronegativity
7. Flame coloration
8. Conductivity
9. Density
10. Hardness
11. Oxidation state
12. Solubility of salts

Atomic radius example of alkaline earth metals

Be(113pm)
Mg(160pm)
Ca(197pm)
Sr(215pm)
Ba(217pm)

Ionization energy example of alkaline earth metals

Be- 900 kJ/mol
Mg- 728 kJ/mol
Ca -690 kJ/mol
Sr-550 kJ/mol
Ba-503 kJ/mol
Ra-509 kJ/mol

Color of Ca in flame coloration

Brick red

Color of Sr in flame coloration

Crimson

Which elements don't give any color in flame coloration and why?

Be and Mg do not give any color to the flame as they have higher ionization potential comparatively others.

Chemical properties of alkaline earth metals

1. Reaction with air
2. Reaction with hydrogen
3. Reaction with water
4. Reaction with acids
5. Reaction with halogens
6. Formation of carbides

Use and application of Be

-never been used
-regarded as one of the most toxic elements for common use

Use and application of Mg

-essential for life
-activator of many enzymes
-neuromuscular functions
Compounds
-Magnesium hydroxide
-Magnesium oxide
-Universal antidote
-Magnesium trisilicate
-talc

Use and application of Ca

-functions of nervous system
-proper cardiac function
-blood clotting
-structural basis of skeleton
Official compounds
-Calcium carbonate
-Calcium chloride
-Calcium gluconate
-Calcium lactate

Use and application of Sr

-adjuvant
-no official compound available

Use and application of Ba

-Barium chloride => very toxic
-Barium ion => produces local irritation
-Barium sulphate => used to help diagnose certain disorders of the esophagus, stomach or intestines

Use and application of Ra

-highly radioactive
-Radiation from radium can destroy living cells
-Radium salts were used to arrest and cure malignant growths

Similarities between alkali metals and alkaline earth metals

1. s-block
2. electropositive
3. great chemical reactivity
4. do not occur in the free state in nature
5. react with water to form metal hydroxides and H2
6. hydroxides give strong bases with water
7. extracted by electrolytic method from their salts
8. silvery in untarnished conditions

Dissimilarities between alkali metals and alkaline earth metals

1. harder, heavier and have higher melting points than alkali metals
2. less basic
3. Ca, Sr, Ba reacts less vigorously with water
4. Carbonate and sulphates
5. Phosphates

explain physical state of alkaline earth metals

-greyish white lustre when cut
-malleable

explain melting and boiling points of alkaline earth metals

-do not show any regular trend
-higher than alkali metals

explain atomic volume, atomic and ionic radii of alkaline earth metals

Because of the addition of an extra shell of electrons to each element from Be to Ra, the atomic volume increases from Be to Ra. With the increases of atomic volume, the atomic and ionic radii (of M2+ ions) also increase from Be to Ra.
The atomic radii of these elements are however smaller than those of alkali metals in the same period. This is since the alkaline earth metals have higher nuclear charge which tends to draw the orbit electrons toward the nucleus.

Explain ionization energies of alkaline earth metals

The first and second ionization energies of these elements decrease with the increase of atomic radii from Be to Ba.

Explain electropositive characters of alkaline earth metals

Although the ionization energies of these elements are higher than those of alkali metals, yet these are sufficiently low to make these metals to lose readily their ns2 electrons to form M2+ ions:
These metals, therefore, show strong electropositive character which increases from Be to Ba. Since these metals have higher ionization energies than the alkali metals, these are not strongly electropositive as the alkali metals.

Explain electronegativities of alkaline earth metals

These are small and decrease from Be to Ba.

Explain flame coloration of alkaline earth metals

In the flame tests Group 2 elements show following color-
Ca- Brick red
Sr- Crimson
Ba- Apple green
Ra- Red
Be and Mg do not give any color to the flame as they have higher ionization potential comparatively others.

Explain conductivity of alkaline earth metals

Since two valence electrons are free to move throughout the metal structure, the alkaline earth metals are good conductors of heat and electricity.

Explain density of alkaline earth metals

These elements have higher density than those of the alkali metals in the same period. Density decreases slightly up to Ca after which it increases.

Explain hardness of alkaline earth metals

These elements are harder than alkali metals.

Explain oxidation state of alkaline earth metals

Alkaline earth metals show +2 oxidation state.

explain solubility of salts of alkaline earth metals

The salts of alkaline earth metals are less soluble than those of alkali metals.

Explain reaction with air of alkaline earth metals

▪The alkaline earth metals react readily on heating with the oxygen (O2) and the nitrogen (N2) of the air to form oxides, MO and nitrides, M3N2.
2M + O2 → 2MO
3M + N2 → M3N2
▪Be reacts less rapidly and requires high temperatures for the formation of BeO.
▪Ba forms peroxides, BaO2, because of its greater activity.
Ba + O2 BaO2

Rate of reactivity, Be < Mg < Ca < Sr < Ba

Explain reaction with hydrogen of alkaline earth metals

▪Mg, Ca, Sr and Ba form hydrides when heated with hydrogen (H2) :
M + H2 → MH2
▪These hydrides readily react with H2O to liberate H2:
MH2 + H2O → M(OH)2 + H2

BeH2 cannot be prepared by the direct combination of Be and H2. It is however, prepared by reducing BeCl2 by LiH and LiAlH4.

BeCl2 + 2LiH BeH2 + 2LiCl

Explain reaction with water of alkaline earth metals

▪Alkaline earth metals react readily with H2O to give hydroxide:
M + 2H2O → M(OH)2 + H2
▪Be does not react with H2O even at elevated temperature. Mg reacts only with steam.

Explain reaction with acids of alkaline earth metals

Alkaline earth metals react vigorously with acids to form corresponding salts:
M + 2HCl → MCl2 + H2

Explain reaction with halogens of alkaline earth metals

Alkaline earth metals react with halogens (X2) to form corresponding halides:
M + X2 → MX2

Explain formation of carbides of alkaline earth metals

When the elements from Mg to Ba or their oxides are heated with carbon, carbides (MC2) are obtained.
Ca + 2C CaC2