Grade 11
  1. Basic concepts of chemistry  1.1. Importance of Chemistry  1.2. Nature and scope of chemistry  1.3. laws of chemical combination  1.3.1. Law of conservation of mass  1.3.2. Law of definite proportions  1.3.3. Law of multiple proportions  1.3.4. Law of gaseous volume  1.3.5. Avogadro's Law  1.4. Dalton's atomic theory  1.5. Mole concept and molar mass  1.6. Percent composition  1.7. Empirical and molecular formula  1.8. Stoichiometry and Stoichiometric Calculations  1.9. Limiting reagent concept
  2. Structure of the atom  2.1. Discovery of the electron, proton, and neutron  2.2. Atomic Model  2.2.1. Thomson's model  2.2.2. Rutherford's model  2.2.3. Bohr's model  2.3. Quantum mechanical model of the atom  2.4. Dual nature of matter and radiation  2.5. Heisenberg's uncertainty principle  2.6. Quantum numbers  2.7. Atomic orbitals and their shapes  2.8. Electronic configuration of elements  2.9. Aufbau principle  2.10. Pauli's exclusion principle  2.11. Hund's maximum multiplicity rule  2.12. de Broglie's hypothesis  2.13. Photoelectric effect
  3. Classification of elements and periodicity in properties  3.1. Historical development of the periodic table  3.2. Modern Periodic Law and Periodic Table  3.3. Periodic trends in properties  3.3.1. Atomic and Ionic Radius  3.3.2. Ionization enthalpy  3.3.3. Electron gain enthalpy  3.3.4. Electronegativity  3.3.5. Valency  3.3.6. Metallic and Non-Metallic Properties  3.3.7. Oxidation states  3.4. Unusual Properties of the First Elements
  4. Chemical Bonding and Molecular Structure  4.1. Kossel–Lewis approach to chemical bonding  4.2. Ionic or electrovalent bond  4.3. Covalent bond and its features  4.4. Bond parameters  4.5. VSEPR Theory  4.6. Valence bond theory  4.7. Hybridization and its types  4.8. Molecular orbital theory  4.8.1. Bond order and stability  4.9. Hydrogen bonding
  5. States of matter  5.1. Intermolecular forces  5.2. Gas Laws  5.2.1. Boyle's law  5.2.2. Charles's Law  5.2.3. Avogadro's Law  5.2.4. Dalton's law of partial pressure  5.2.5. Graham's law of spread  5.3. Ideal Gas Equation and Applications  5.4. Real gases and deviations from ideal behaviour  5.5. Kinetic molecular theory of gases  5.6. Liquefaction of gases  5.7. Properties of Liquids  5.8. Surface tension and viscosity
  6. Thermodynamics  6.1. System and environment  6.2. Types of systems in thermodynamics  6.3. Types of procedures  6.4. First law of thermodynamics  6.5. Internal energy and enthalpy  6.6. Heat capacity and specific heat  6.7. Hess's law of constant heat summation  6.8. Bond dissociation enthalpy  6.9. Enthalpy of formation and combustion  6.10. Enthalpy of solution and neutralization  6.11. Spontaneity and the second law of thermodynamics  6.12. Gibbs free energy and its applications
  7. Balance  7.1. The concept of balance  7.2. Equilibrium constant and its applications  7.3. Le Chatelier's principle  7.4. Ionic equilibrium in solutions  7.5. Acid and Base Theory  7.5.1. Arrhenius concept  7.5.2. Bronsted-Lowry concept  7.5.3. Lewis concept  7.6. pH Scale and pOH  7.7. Common ion effect  7.8. Hydrolysis of salts  7.9. Buffer solutions and their mechanism of action  7.10. Solubility equilibrium of sparingly soluble salts
  8. Redox reactions  8.1. Oxidation and reduction concepts  8.2. Oxidation number and its applications  8.3. Redox reactions in terms of electron transfer  8.4. Balancing redox reactions (oxidation number and ion-electron methods)  8.5. Types of redox reactions  8.6. Electrochemical Cells and Redox Reactions
  9. Hydrogen  9.1. Position of Hydrogen in the Periodic Table  9.2. Isotopes of hydrogen  9.3. Preparation of Hydrogen  9.4. Properties of Hydrogen  9.5. Hydrides and their classification  9.6. Water and heavy water  9.7. Hydrogen peroxide and its properties  9.8. Uses of Hydrogen and Its Compounds
  10. S-block elements (alkali and alkaline earth metals)  10.1. Group 1 Elements - Properties and Trends  10.2. Group 2 Elements - Properties and Trends  10.3. Unusual properties of lithium and beryllium  10.4. Important compounds of sodium and their uses  10.5. Important Compounds of Magnesium and Calcium
  11. Some p-block elements  11.1. General Introduction to p-Block Elements  11.2. Group 13 Elements  11.2.1. Boron and its compounds  11.3. Group 14 Elements  11.3.1. Carbon and its allotropes  11.3.2. Important Compounds of Carbon and Silicon
  12. Organic Chemistry - Some Basic Principles and Techniques  12.1. Classification and Nomenclature of Organic Compounds  12.2. Structural representation of organic compounds  12.3. Classification of organic reactions  12.4. Electronic Effects in Organic Chemistry  12.4.1. Inductive effect  12.4.2. Resonance effect  12.4.3. Hyperconjugation  12.5. Reaction mechanism and intermediate species  12.6. Purification and qualitative analysis of organic compounds
  13. Hydrocarbons  13.1. Hydrocarbons  13.1.1. Preparation and Properties of Alkenes  13.2. alkene  13.2.1. Preparation and Properties of Alkenes  13.2.2. Electrophilic addition reactions  13.3. Alkynes  13.3.1. Preparation and Properties of Alkynes  13.4. Aromatic hydrocarbons  13.4.1. Structure and properties of benzene  13.4.2. Electrophilic substitution reactions of benzene
  14. Environmental Chemistry  14.1. Environmental Pollution  14.2. Atmospheric pollution and the greenhouse effect  14.3. Water pollution and treatment methods  14.4. Soil pollution and its effects  14.5. Industrial waste and its treatment  14.6. Strategies for pollution control

Grade 11 → States of matter → Gas Laws ↓


Graham's law of spread


Graham's law of diffusion is a principle in chemistry that describes the behavior of gases. In simple terms, it tells us that lighter gases diffuse, or spread out, faster than heavier gases when they are allowed to mix. This behavior is based on the principle that gas molecules are in constant random motion. When gases meet, the molecules collide with each other and diffuse out. Understanding this law helps us understand how gases behave under different conditions and is a fundamental concept in chemistry.

Understanding the spread

Diffusion is the process by which molecules spread from areas of high concentration to areas of low concentration. In the context of gases, this means how gas molecules move and mix with each other. For example, when you open a bottle of perfume in a room, the scent quickly spreads throughout the space. This is due to diffusion.

Consider the above example. If each coloured circle represents a different gas molecule, diffusion represents how these coloured circles will spread out uniformly on the line given enough time. Initially, they are far apart, but through random motion, they will eventually fill the space uniformly.

Mathematical expression of Graham's law

Graham's Law provides a quantitative relationship between the rate of diffusion of gases and their molar masses. The mathematics behind Graham's Law can be described using the following equation:

rate of diffusion of gas 1 / rate of diffusion of gas 2 = sqrt(M₂ / M₁)

Here:

  • rate of diffusion of gas 1 is how fast the first gas diffuses.
  • rate of diffusion of gas 2 is how quickly the second gas diffuses.
  • M₁ is the molar mass of the first gas.
  • M₂ is the molar mass of the second gas.

The equation tells us that the rate of diffusion of a gas is inversely proportional to the square root of its molar mass. This means that lighter gases diffuse faster than heavier gases.

Example calculation

Let's consider an example to illustrate Graham's law. Suppose we have two gases: hydrogen (H₂) and oxygen (O₂). The molar mass of hydrogen is about 2 g/mol, and for oxygen, it is about 32 g/mol. We want to know how fast hydrogen diffuses compared to oxygen.

rate of diffusion of H₂ / rate of diffusion of O₂ = sqrt(32 / 2) = sqrt(16) = 4

This calculation shows that hydrogen expands 4 times faster than oxygen. Since hydrogen is much lighter than oxygen, it expands more rapidly when the two gases are allowed to mix.

Visualization of spread rates

Consider a simple visualization of gas diffusion rates. Imagine two connected chambers with a barrier between them. Initially, one chamber is filled with hydrogen and the other with oxygen. When the barrier is removed, diffusion occurs.

Hydrogen Oxygen

Over time, hydrogen gas enters the oxygen chamber more rapidly than oxygen, allowing for a more uniform distribution of gases for hydrogen.

Applications of Graham's Law

Graham's Law has many practical applications. It is used in areas ranging from industrial processes to medical treatments. Some of the major applications include:

1. Separation of gases: Graham's law is used in processes such as gas chromatography, where different gases are separated based on their rate of diffusion.

2. Respiratory System: In human physiology, the diffusion of gases in the lungs follows Graham's law as oxygen and carbon dioxide are exchanged.

3. Effusion: This is a related concept where gas escapes through a small hole. Graham's law can predict the rate of effusion based on the molar mass of the gases.

Textual example of gas expansion

Consider a real-world scenario: You are in the kitchen with a pot of boiling water. As the water vapor (steam) rises, it mixes with the air in the kitchen, which is primarily nitrogen and oxygen. Because water vapor is relatively light, it spreads quickly through the kitchen air, creating a humid environment.

Let's apply Graham's Law here. Suppose you compare the diffusion rates of water vapor and carbon dioxide (CO₂). Water vapor has a molar mass of about 18 g/mol while carbon dioxide has a molar mass of about 44 g/mol. We can use Graham's Law to figure out how the diffusion rates of these gases compare.

rate of diffusion of H₂O / rate of diffusion of CO₂ = sqrt(44 / 18) = sqrt(2.44) = 1.56

This calculation shows that water vapor diffuses about 1.56 times faster than carbon dioxide under the same conditions.

Conclusion

Graham's diffusion law provides a fundamental understanding of how gases behave when they mix together. It is not only essential for theoretical chemistry, but also has practical implications in many fields. By investigating how the mass of gas molecules affects their diffusion rates, we gain deep insights into natural processes and can apply this knowledge to technological and industrial applications.


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Graham's law of spread

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