Comprehensive Study Guide & Interactive Quiz • @everexams.com
Environmental chemistry is a special area of chemistry that examines how chemicals interact in the environment and affect living things. It deals with the study of chemical processes happening in Earth’s environment and their direct or indirect impact on organisms that live on Earth.
Acronym: Remember “CHEM” – Chemicals, Human impact, Environment, Monitoring. Environmental chemistry studies chemicals in the environment, their human impact, environmental fate, and requires monitoring.
The presence of undesirable substances in the environment that harm the natural balance of ecosystems is known as environmental pollution. There are several types of pollution that can negatively impact the environment and human health such as air pollution, water pollution, soil pollution, noise pollution, radioactive pollution, etc.
Earth’s environment consists of four interconnected parts that work together to sustain life:
Sentence Mnemonic: “Little Happy Babies Always” – Lithosphere, Hydrosphere, Biosphere, Atmosphere. Visualize Earth with these four layers supporting happy babies (life).
The Earth’s atmosphere is divided into four major regions based on variation in temperature and composition:
Acronym: “The Smart Man Travels” – Troposphere, Stratosphere, Mesosphere, Thermosphere. Remember temperatures decrease in Troposphere and Mesosphere, increase in Stratosphere and Thermosphere.
The troposphere is the lowest layer of Earth’s atmosphere, where we experience our daily weather conditions such as rain, snow, winds, storms, thunders, and clouds. The temperature in this region decreases constantly with increasing altitude from approximately 15°C to -56°C.
This region plays a vital role in supporting life on Earth as it holds a significant portion of oxygen, carbon dioxide, and water vapors which are essential for the sustenance of living organisms.
Certain toxic substances, including nitrogen oxides (NOx), sulphur oxides (SOx), volatile organic compounds (VOCs), and ozone (O₃) can cause atmospheric pollution.
Carbon Monoxide (CO): Toxic gas with great affinity for hemoglobin. Released by partial combustion of fuel in automobiles, petroleum refining, and forest fires. In troposphere, it’s broken down by UV radiation into free carbon particles responsible for smog formation.
Carbon Dioxide (CO₂): Added to atmosphere due to combustion of fossil fuels. Increase causes suffocation and respiratory disorders.
Mainly nitric oxide (NO) and nitrogen dioxide (NO₂). Produced from combustion of fuel at high temperature. Harmful because they form acid rain and ozone in the atmosphere.
Remember sources: CO from incomplete combustion, CO₂ from complete combustion. NOx from high temperature combustion (cars, power plants). Visualize car exhaust for all three pollutants.
Burning of gasoline in car engines produces CO, NO, and unburnt hydrocarbons. Catalytic converters transform these harmful chemicals into less harmful substances like CO₂, N₂, O₂, and H₂O. They contain platinum and palladium as catalysts.
Catalytic Converter Reactions: CO → CO₂, NOx → N₂, Hydrocarbons → CO₂ + H₂O. Remember “3 Cs” – Converts, Catalyzes, Cleans. Pt/Pd metals are used as catalysts.
Smog is a combination of smoke and fog. Industrial smog is a mixture of SO₂, aerosols and volatile organic compounds, forming a brown-yellow layer in industrial areas. It has harmful effects on human health, plant growth, and is a major contributor to environmental pollution.
Global warming refers to the gradual rise in Earth’s average surface temperature. Greenhouse gases (CH₄, CO₂, N₂O, H₂O) regulate Earth’s temperature by absorbing IR radiation and re-emitting it towards Earth’s surface.
Consequences include melting glaciers, rising sea levels, acid rain, irregular crop patterns, and changes in human lifestyle.
Greenhouse Gases: Remember “CHOaN” – CH₄, H₂O, O₃, CO₂, N₂O. Visualize a greenhouse with these gases trapping heat like glass.
Acid rain refers to rainfall that has acidic components such as nitric acid, sulphuric acid, and carbonic acid. Normal rainfall pH: 6-6.5; Acid rain pH: below 5.
Formation: SO₂ + H₂O → H₂SO₄; NOx + H₂O → HNO₃; CO₂ + H₂O → H₂CO₃
Effects: Increases acidity of rivers, reduces soil fertility, causes corrosion of buildings, makes groundwater toxic.
Acid Rain Components: “SUN” – Sulphuric, Nitric, Carbonic acids. Sources: “SCN” – Sulphur oxides, Carbon oxides, Nitrogen oxides.
The stratosphere extends from 11km to 50km above Earth’s surface and contains the ozone (O₃) layer. This layer absorbs harmful UV radiation from the sun, making life on Earth possible.
Ozone Layer Location: Stratosphere (NOT Troposphere). Remember “Ozone is a STRONG shield in the STRATOSPHERE” – both start with “STR”.
Formation: O₂ + UV → O• + •O; O• + O₂ → O₃
Natural Balance: Ozone is constantly produced and destroyed by solar energy, maintaining equilibrium in the stratosphere.
Human Impact: Ozone depletion occurs through ozone-depleting substances (ODS) like chlorofluorocarbons (CFCs).
CFCs are stable gases used as coolants in refrigeration and as propellants in aerosol sprays. In the stratosphere, UV radiation breaks them down releasing chlorine atoms that catalyze ozone destruction.
Reaction: Cl• + O₃ → ClO• + O₂; ClO• + O₃ → Cl• + 2O₂
Alternative: Hydrofluorocarbons (HFCs) which don’t contain chlorine and don’t deplete ozone.
CFC Destruction: Remember “Cl kills O₃” – Chlorine from CFCs destroys ozone. One Cl atom can destroy up to 100,000 ozone molecules! Visualize chlorine as “ozone eater”.
Any undesirable change in water quality that adversely affects life is water pollution. Pollutants are classified into:
Small solid particles that remain suspended (colloids) or settle down (sediments). Cause turbidity and reduce sunlight for aquatic life.
Inorganic (minerals, salts, metal cations) and organic (from decomposition) solids that dissolve in water.
Four types of tests performed on water samples:
WHO Standards Mnemonic: “Pretty Clean Water Tastes Delicious” – pH, Chlorine, Water quality, Turbidity, Dissolved solids. Remember key values: pH 6.5-8.5, TDS < 600, Turbidity < 5.
Green chemistry is the design and development of processes that minimize or eliminate the use of hazardous chemicals. It aims to create safer chemicals and environmentally friendly processes.
Green Chemistry Focus: Remember “3 Rs” – Reduce waste, Renewable resources, Real-time analysis. Atom economy means maximum atoms from reactants end up in product.
(d) Carbon dioxide (CO₂) – CO₂ is a major greenhouse gas that traps heat in the atmosphere. Other greenhouse gases include CH₄, N₂O, and H₂O vapor.
(c) Below 5 – Normal rainfall has pH 6-6.5, but acid rain has pH below 5 due to acidic components like H₂SO₄, HNO₃, and H₂CO₃.
(d) Chlorofluorocarbons (CFCs) – CFCs release chlorine atoms that catalytically destroy ozone molecules in the stratosphere.
(b) Stratosphere – The stratosphere (11-50 km) contains the ozone layer that protects Earth from harmful UV radiation.
(c) Greenhouse gases emission – Human activities increasing greenhouse gases (CO₂, CH₄, N₂O) are the main cause of recent global warming.
(d) Developing environmentally friendly chemicals – Green chemistry focuses on designing safer chemicals and processes that minimize environmental impact.
(b) Smoke and fog – The term ‘smog’ comes from combining ‘smoke’ and ‘fog’. Industrial smog contains SO₂, aerosols and VOCs.
(a) Pt and Pd – Platinum and palladium are noble metals used as catalysts in catalytic converters to convert harmful gases to less harmful ones.
(b) Stratosphere – The ozone layer is located in the stratosphere, approximately 15-35 km above Earth’s surface.
(c) Industrial activities – Industrial discharge containing chemicals, heavy metals, and waste is a primary source of water pollution.
Four atmospheric segments: Troposphere, Stratosphere, Mesosphere, Thermosphere.
We live in: Troposphere (the lowest layer, 0-11 km above Earth’s surface, where weather occurs and contains the air we breathe).
Causes of ozone depletion:
Industrial smog: A type of air pollution that is a mixture of smoke and fog, appearing as a brown-yellow layer in industrial areas.
Formation:
Main greenhouse gases:
Four fundamental wastewater testing methods:
Effects on human health:
Prevention measures:
Main cause of Global warming: Enhanced greenhouse effect due to increased atmospheric concentrations of greenhouse gases (CO₂, CH₄, N₂O) from human activities like burning fossil fuels, deforestation, agriculture, and industrial processes.
Effects on weather patterns:
Chemistry of nitrogen oxides (NOx) in troposphere:
Chemistry of sulphur oxides (SOx) in troposphere:
Greenhouse effect: Natural process where certain gases in Earth’s atmosphere trap heat from the sun, keeping the planet warm enough to support life. Sunlight passes through atmosphere, warms Earth’s surface, which then emits infrared radiation. Greenhouse gases absorb this radiation and re-emit it in all directions, including back toward Earth, warming the surface.
Human enhancement of greenhouse effect:
Since industrial revolution, atmospheric CO₂ has increased from 280 ppm to over 420 ppm, causing enhanced greenhouse effect and global warming.
Ozone Depleting Substances (ODS): Chemicals containing chlorine or bromine that destroy stratospheric ozone. They are stable in lower atmosphere but break down in stratosphere releasing halogen atoms that catalyze ozone destruction.
Major ODS:
Human activities contributing to ozone depletion:
The 1987 Montreal Protocol successfully phased out most ODS, allowing ozone layer recovery.
Catalytic converter: An emissions control device installed in vehicle exhaust systems that converts toxic gases and pollutants in exhaust gas into less toxic pollutants through catalyzed chemical reactions.
Structure and function:
Main pollutants targeted:
Types:
Catalytic converters reduce emissions by 90% for CO and HC, and 70-90% for NOx when functioning properly.
1. Start with understanding basic concepts before diving into reactions.
2. Create concept maps connecting different types of pollution and their effects.
3. Use mnemonics and acronyms to remember lists and sequences.
1. Allocate specific time slots for each environmental chemistry topic.
2. Practice with past papers and quizzes regularly.
3. Review difficult concepts multiple times using spaced repetition.
1. Create visual diagrams of atmospheric layers and pollution cycles.
2. Associate chemical names with real-world examples (e.g., CO with car exhaust).
3. Use flashcards for key terms and their definitions.
1. Focus on understanding rather than rote memorization.
2. Practice writing balanced chemical equations for pollution formation.
3. Review numerical problems related to pH, concentration, and standards.
1. Relate concepts to current environmental issues in the news.
2. Understand the connection between human activities and environmental changes.
3. Explore case studies of environmental disasters and their chemical causes.
1. Teach concepts to someone else to reinforce your understanding.
2. Create summary sheets for each major topic.
3. Regularly test yourself with quizzes and recall exercises.
Master Environmental Chemistry with the “3C Approach”:
Connect concepts across topics (e.g., how smog relates to both troposphere chemistry and health effects).
Correlate chemical reactions with real-world phenomena (e.g., acid rain with building corrosion).
Consolidate knowledge through regular practice and application.