Graduate
  1. Physical Chemistry  1.1. Thermodynamics  1.1.1. Laws of Thermodynamics  1.1.2. Enthalpy and heat capacity  1.1.3. Entropy and free energy  1.1.4. Phase Equilibrium  1.1.5. Statistical thermodynamics  1.1.6. Thermodynamic cycle  1.1.7. Fugacity and activity  1.2. Quantum Chemistry  1.2.1. Principles of quantum mechanics  1.2.2. Schrödinger Equation  1.2.3. Particle in a box  1.2.4. Operators and eigenvalues  1.2.5. Atomic orbitals  1.2.6. Molecular orbital theory  1.2.7. Perturbation theory  1.2.8. Valence bond theory  1.2.9. Hybridization and chemical bonding  1.3. Chemical kinetics  1.3.1. Rate laws and reaction mechanisms  1.3.2. Collision theory  1.3.3. Transition state theory  1.3.4. Enzyme Kinetics  1.3.5. Chain Reactions and Polymerization  1.3.6. Photochemical reactions  1.4. Statistical mechanics  1.4.1. Partitioning functions  1.4.2. Molecular distribution functions  1.4.3. Boltzmann Distribution  1.4.4. Bose–Einstein and Fermi–Dirac statistics  1.5. Spectroscopy  1.5.1. Rotational Spectroscopy  1.5.2. Vibrational Spectroscopy  1.5.3. Electronic Spectroscopy  1.5.4. Nuclear magnetic resonance spectroscopy  1.5.5. Mass Spectrometry  1.5.6. Raman Spectroscopy  1.5.7. Electron paramagnetic resonance spectroscopy  1.6. Surface and colloidal chemistry  1.6.1. Absorption isotherm  1.6.2. Surface tension and wetting  1.6.3. Colloidal Stability  1.6.4. Catalysis  1.6.5. Emulsions and micelles  1.7. Electrochemistry  1.7.1. Nernst equation  1.7.2. Electrochemical cells  1.7.3. Conductivity and mobility  1.7.4. War  1.7.5. Fuel cells  1.7.6. Electrolysis
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic reactions  2.2. Spectroscopy and structural determination  2.2.1. UV-Vis Spectroscopy  2.2.2. IR Spectroscopy  2.2.3. NMR Spectroscopy  2.2.4. Mass Spectrometry  2.2.5. X-ray crystallography  2.3. Stereoscopic  2.3.1. Chirality and optical activity  2.3.2. Structural analysis  2.3.3. Geometrical isomerism  2.3.4. Dynamic Stereochemistry  2.4. Organometallic Chemistry  2.4.1. Organolithium and organomagnesium reagents  2.4.2. Palladium-catalyzed cross-coupling reactions  2.4.3. Transition Metal Complexes  2.4.4. Metal–carbon bond  2.5. Polymer chemistry  2.5.1. Polymerization mechanism  2.5.2. Polymer Characteristics  2.5.3. Biodegradable Polymer  2.5.4. Conducting polymer  2.5.5. Supramolecular polymers  2.6. Medicinal chemistry  2.6.1. Drug design and development  2.6.2. Pharmacokinetics and pharmacodynamics  2.6.3. Structure-activity relationships  2.6.4. Molecular docking and drug screening
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Crystal field theory  3.1.2. Ligand field theory  3.1.3. Spectrochemical Series  3.1.4. Chelation and stability  3.2. Organometallic Chemistry  3.2.1. Metal Carbonyls  3.2.2. Catalysis by organometallic complexes  3.2.3. Metallocenes  3.3. Bio-inorganic chemistry  3.3.1. Metalloproteins and enzymes  3.3.2. The role of metals in biological systems  3.3.3. Metal ion transport and storage  3.4. Solid state chemistry  3.4.1. Crystal Structures  3.4.2. Band theory of solids  3.4.3. Superconductors  3.4.4. Defects in the crystal  3.5. Lanthanides and Actinides  3.5.1. Electronic configuration in lanthanides and actinides  3.5.2. Coordination chemistry of the lanthanides  3.5.3. Magnetic Properties of Lanthanides
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.2. Spectroscopic Techniques  4.2.1. Atomic absorption spectroscopy  4.2.2. X-ray diffraction  4.2.3. Inductively coupled plasma spectroscopy  4.3. Electroanalytical methods  4.3.1. Potentiometry  4.3.2. Voltammetry  4.3.3. Colometry  4.4. Mass Spectrometry  4.4.1. Ionization Technique  4.4.2. Fragmentation Pattern  4.5. Chemometrics  4.5.1. Multidisciplinary analysis  4.5.2. Machine Learning in Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.1.1. Force fields and energy minimization  5.1.2. Monte Carlo simulation in molecular dynamics simulations  5.2. Quantum chemical methods  5.2.1. Hartree–Fock theory  5.2.2. Density functional theory  5.2.3. Semi-empirical methods  5.3. Computational drug design  5.3.1. Molecular Docking  5.3.2. QSAR Modeling  5.3.3. Virtual Screening
  6. Biochemistry  6.1. Enzyme Kinetics  6.1.1. Michaelis-Menten kinetics  6.1.2. Inhibition mechanism  6.2. Metabolism and Bioenergetics  6.2.1. Glycolysis  6.2.2. Citric acid cycle  6.2.3. Electron transport chain  6.3. molecular Biology  6.3.1. DNA replication and repair  6.3.2. Protein synthesis  6.3.3. Gene Regulation  6.4. Structural Biochemistry  6.4.1. Protein Folding  6.4.2. Membrane Biophysics
  7. Environmental Chemistry  7.1. Atmospheric Chemistry  7.1.1. Greenhouse gases  7.1.2. Ozone depletion  7.1.3. Air pollutants and smoke  7.2. Water Chemistry  7.2.1. pH and water hardness  7.2.2. Wastewater treatment  7.2.3. Aquatic Chemistry  7.3. Soil Chemistry  7.3.1. Heavy metal contamination  7.3.2. Soil pH and Buffering  7.3.3. Nutrient cycling  7.4. Toxicology and Chemical Safety  7.4.1. Toxicokinetics  7.4.2. Risk Assessment in Toxicology and Chemical Safety in Environmental Chemistry  7.4.3. Effects of pollutants on the environment

Graduate → Environmental Chemistry ↓


Water Chemistry


Water chemistry is an important part of environmental chemistry because it deals with understanding the chemical properties and processes of water in various environmental contexts. This includes natural water bodies such as rivers, lakes, and oceans, as well as water in artificial settings such as treatment plants and distribution systems. Understanding water chemistry allows scientists to assess water quality, understand geochemical cycles, and address issues of pollution and environmental sustainability.

Chemical composition of water

Water, which has the chemical formula H2O, is a simple molecule composed of two hydrogen atoms and one oxygen atom. The structure of water is bent rather than linear because of the two pairs of lone electrons on the oxygen atom. The angle between the hydrogen atoms is approximately 104.5 degrees. This unique angular structure is important for many of water's properties.

Below is a simplified illustration of a water molecule:

        Hey
       ,
      HH

Properties of water

Difference of opinion

Water is known for its polarity. The oxygen atom is more electronegative than the hydrogen atoms, which means it has a stronger tendency to attract electrons towards itself. This creates a dipole moment, with a partial negative charge near the oxygen atom and a partial positive charge near the hydrogen atoms.

Hydrogen bonding

The polarity of water molecules allows them to form hydrogen bonds with each other. These are weaker bonds than covalent bonds, but are significant in number, leading to phenomena such as water's high boiling point and surface tension.

Solvent properties

Because of its polarity, water is known as the "universal solvent." It can dissolve many substances, including salts, sugars, acids, bases, and gases. This makes water an excellent medium for chemical reactions and biological processes.

pH of water

The pH value of water is a measure of its acidity or alkalinity, ranging from 0 to 14. Pure water has a neutral pH value of 7. However, the pH of natural water can vary depending on dissolved minerals and gases.

The pH scale is represented as:

        Acidic (0-6) Neutral (7) Alkaline (8-14)

Changes in the pH of water can affect aquatic life and influence chemical reactions. For example, acidic water can lead to harmful conditions such as corrosion and metal toxicity for aquatic life.

Hardness and mineral composition

Water hardness is determined by the concentration of calcium and magnesium ions. "Hard water" has high levels of these minerals, while "soft water" has low levels. Hardness is often measured in parts per million (ppm).

Following are the chemical reactions leading to formation of hard water:

        CaCO3 + CO2 + H2O ⇌ Ca2+ + 2HCO3-

The presence of calcium carbonate and magnesium carbonate in water is often due to geological structures and clay content, which affect the chemistry of water systems.

Water hardness can affect the usability of water for domestic, industrial, and agricultural purposes. For example, hard water can cause scaling in pipes and reduce the effectiveness of soaps and detergents.

Natural water systems

Rivers and streams

Rivers and streams are dynamic aquatic systems, with varying chemistries depending on their source, flow rate, and environmental influences. They transport dissolved and particulate matter, affecting the ecosystems they cross.

The chemistry of river water is often classified based on its components, including:

  • Dissolved gases such as oxygen and carbon dioxide
  • Inorganic ions such as sodium, potassium, and chloride
  • Organic compounds obtained from both natural and anthropogenic sources

Lakes and reservoirs

Lakes and reservoirs are stagnant water bodies with varying depths and stratification layers. They exhibit complex chemical interactions influenced by temperature, light penetration, and biological activities.

Seasonal changes in lakes can redistribute nutrients and dissolved gases, affecting water quality and aquatic life:

The basic model of thermal stratification in a lake includes the following:

        epilimnion (warm upper layer)
        Thermocline (middle layer with temperature gradient)
        hypolimnion (cold bottom layer)

Ocean

Oceans are vast bodies of salt water that contain high levels of dissolved salts, primarily sodium chloride. The chemistry of ocean water is important for global climate regulation and marine life.

The salinity of seawater is normally around 35 parts per thousand (ppt), affected by factors such as evaporation, the amount of freshwater, and geological activity.

Water treatment and quality

Water treatment processes are used to make water safe for human consumption and environmental health. These include methods such as sedimentation, filtration, and disinfection.

Sedimentation

This process involves removing suspended particles from the water through gravity. Chemicals such as alum may be added to help form larger particles known as floc.

Filtration

Filtration involves passing water through materials such as sand or granular activated carbon, removing remaining impurities and particulate matter.

Disinfection

Disinfection methods are used to kill or inactivate harmful microorganisms. Common disinfectants include chlorine, ozone, and ultraviolet light.

Pollution and environmental impact

Water pollution is a significant environmental concern, as pollutants from industrial, agricultural and domestic sources affect water systems in a variety of ways.

Common pollutants include:

  • Nutrients such as nitrates and phosphates that cause eutrophication
  • Heavy metals such as lead, mercury, and cadmium
  • Organic pollutants such as oils and detergents

Eutrophication

Eutrophication is a process in which an excess of nutrients in aquatic systems causes excessive growth of plants and algae. This can result in a lack of oxygen and affect aquatic life.

Acid rain

Acid rain caused by emissions of sulfur dioxide and nitrogen oxides leads to acidification of water bodies, affecting the integrity of ecosystems and solids.

Conclusion

Water chemistry is a complex and multidisciplinary field that involves the study of chemical processes and properties in various water systems. Understanding water chemistry makes it possible to monitor, manage, and improve water quality, thereby aiding in environmental protection and human health protection. Continued research and technological innovation are critical to address water-related challenges and ensure sustainability for future generations.


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Water Chemistry

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