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 ↓


Dalton's law of partial pressure


Dalton's law of partial pressures is one of the fundamental laws of gases discovered in the early 19th century. It is named after the English chemist and physicist John Dalton, who formulated the law. Understanding Dalton's law requires a basic understanding of the behavior of gases, especially when they are mixed in a confined space.

Understanding the basics

Unlike solids and liquids, gases have no definite shape or volume. They expand to fill the container they are in. The behaviour of gases can be described using various gas laws, which collectively form the basis of understanding physical chemistry and gaseous states.

Dalton's law of partial pressure deals with the pressure exerted by a mixture of non-reactive gases. This law states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each individual gas in the mixture.

Mathematical representation

The mathematical statement of Dalton's law can be expressed as follows:

P_total = P_1 + P_2 + P_3 + ... + P_n

Here, P_total represents the total pressure of the gas mixture, while P_1, P_2, P_3, and P_n represent the partial pressures of individual gases in the mixture.

This formula assumes that the gases do not react chemically with each other, i.e., they behave like ideal gases, and that the temperature remains constant throughout the system.

What is partial pressure?

Partial pressure is the pressure that a gas present in a mixture would exert if it alone occupied the entire volume at the same temperature. It represents the individual contribution of any one gas to the total pressure of the system.

Example 1

Imagine that you have a container with three gases - oxygen, nitrogen and carbon dioxide. If the partial pressures of these gases are 200 atm, 500 atm and 300 atm, respectively, then according to Dalton's law, the total pressure in the container is:

P_total = P_O2 + P_N2 + P_CO2
P_total = 200 atm + 500 atm + 300 atm
P_total = 1000 atm

Applications and significance

Dalton's law of partial pressure is important in various fields such as chemistry, physics, biology, and engineering. It helps in studying the behavior of gases and is applicable in many practical situations. Here are some important applications and cases:

  • Understanding the behaviour of gases in chemical reactions, particularly reactions that occur in the gas phase.
  • In the medical field, regulating gas mixtures for anesthetic purposes.
  • Calculating the composition of gases in environmental studies, such as determining the components of air.
  • It is used by divers to understand how different gases behave under high pressure conditions underwater, which is essential for the prevention of illnesses such as decompression sickness.
  • In industrial gas supply and distribution, Dalton's law helps to verify the composition of gas mixtures.

Visual example

Consider a simple system where three different gases are contained in three connected cylinders. Each cylinder contains one gas (A, B, and C), and each contributes uniquely to the total pressure of the system.

Gas A : PA Gas B : PB Gas C: PC Total pressure = PA + PB + PC

In this diagram, each rectangle represents a gas present within the system. According to Dalton's law, when these gases are mixed together, the total pressure exerted by them is the sum of the pressures that each gas would exert if it alone occupied the entire volume.

Derivation of Dalton's law

Dalton's law can also be argued from the kinetic molecular theory which proposes that:

  • Gases are made up of tiny particles moving around randomly.
  • These particles are negligibly small compared to the volume of the gas.
  • There is no force acting between the gas particles, and the collision between them is perfectly elastic.

From these postulates it can be concluded that in a mixture of non-reactive gases, the behavior of each gas is unaffected by the other gases. This behavior extends naturally to pressure: each gas contributes to the overall pressure as if it were the only gas present. Therefore, the combined pressure of the mixed gases is simply the sum of their individual pressures.

Text examples and exercises

Example 2

If you have a mixture of helium, argon, and neon gases with partial pressures of 150 atm, 300 atm, and 200 atm, respectively, what is the total pressure?

P_total = P_He + P_Ar + P_Ne
P_total = 150 atm + 300 atm + 200 atm = 650 atm

Exercise

Solve the following problems based on Dalton's law:

  1. A container contains a mixture of three gases: hydrogen, oxygen and nitrogen. The partial pressures of the gases are 250 atm, 400 atm and 350 atm, respectively. Calculate the total pressure within the container.
  2. A cylinder contains a mixture of four non-reactive gases: A, B, C, and D. Given that the partial pressures are, PA = 100 mmHg, PB = 150 mmHg, PC = 200 mmHg, and PD = 250 mmHg. Find the total pressure in mmHg.
  3. Consider a scenario where the total pressure exerted by a gaseous mixture is 950 atm. If the partial pressures of two gases are 300 atm and 350 atm, find the partial pressure of the third gas in the mixture.

Conclusion

Dalton's law of partial pressures provides a simple method for understanding and calculating the behavior of gas mixtures. It describes how gases combine and contribute to the total pressure within a system. This concept is not just theoretical, but finds practical applications in many scientific and industrial processes. As you continue to study, remember that Dalton's law assumes ideal conditions, real-world scenarios may introduce deviations, but the fundamental principle provides an excellent basis for approaching and solving complex problems involving gases.

By mastering Dalton's Law, you gain valuable insight into understanding more complex chemical behavior and its practical applications in fields ranging from medicine to environmental science.


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Dalton's law of partial pressure

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