Grade 10
  1. Matter and its properties  1.1. States of matter  1.2. Physical and chemical properties of matter  1.3. Classification of substances (elements, compounds, mixtures)  1.4. Changes in Matter (Physical and Chemical Changes)  1.5. Law of conservation of mass and law of definite proportions
  2. Atomic Structure  2.1. Historical development of the atomic model  2.2. Subatomic particles (protons, neutrons, electrons)  2.3. Atomic number, mass number and isotopes  2.4. Electronic Configuration and Energy Levels  2.5. Valency, ion formation and oxidation state
  3. Periodic table  3.1. History and Development of the Periodic Table  3.2. Modern Periodic Law and Periodic Trends  3.3. Groups and Periods in the Periodic Table  3.4. Trends in the Periodic Table  3.5. Metals, non-metals, metalloids and their properties  3.6. Noble gases and their chemical inertness
  4. Chemical bond  4.1. Formation of Chemical Bonds (Octet Rule)  4.2. Ionic Bonding and Properties of Ionic Compounds  4.3. Covalent Bond and Properties of Covalent Compounds  4.4. Metallic bond and its properties  4.5. Molecular geometry and VSEPR theory  4.6. Polarity and dipole moment of molecules  4.7. Intermolecular forces
  5. Chemical Reactions and Equations  5.1. Types of Chemical Reactions  5.2. Writing and balancing chemical equations  5.3. Law of conservation of mass in chemical reactions  5.4. Factors Affecting Chemical Reactions  5.5. Catalysts and their role in chemical reactions  5.6. Exothermic and Endothermic Reactions
  6. Stoichiometry and Chemical Calculations  6.1. Mole concept and Avogadro number  6.2. Molar Mass and Gram-Mole Conversions  6.3. Empirical and molecular formula  6.4. Stoichiometric calculations and chemical yield  6.5. Limiting and Excess Reactants
  7. Acids, Bases and Salts  7.1. Properties and Definitions of Acids and Bases (Arrhenius, Bronsted-Lowry, Lewis)  7.2. pH Scale, pOH, and Indicators  7.3. Neutralization reactions and salt formation  7.4. Strength of Acids and Bases (Strong vs. Weak Acids and Bases)  7.5. Common Acids and Bases in Daily Life  7.6. Salts, their solubility and applications
  8. Metals and Nonmetals  8.1. Physical and chemical properties of metals  8.2. Physical and Chemical Properties of Non-Metals  8.3. Reactivity Series of Metals and Displacement Reactions  8.4. Extraction of metals from ores  8.5. Corrosion, its causes and prevention  8.6. Alloys, their composition and uses
  9. Carbon and its compounds  9.1. Allotropes of Carbon  9.2. Hydrocarbons and their classification (alkanes, alkenes, alkynes)  9.3. Functional groups in organic compounds  9.4. Nomenclature of organic compounds (IUPAC system)  9.5. Isomerism in organic chemistry (structural and geometrical)  9.6. Important organic reactions (combustion, addition, substitution, polymerization)  9.7. Applications of organic compounds in industry and daily life
  10. Environmental Chemistry  10.1. Air Pollution (Sources, Effects and Control)  10.2. Water Pollution (Causes, Effects and Remedies)  10.3. Greenhouse effect and global warming  10.4. Ozone layer depletion and its effects  10.5. Green Chemistry and Its Applications  10.6. sustainable chemistry practice
  11. Thermochemistry  11.1. Heat and Energy Changes in Chemical Reactions  11.2. Exothermic and Endothermic Reactions  11.3. Enthalpy, enthalpy change, and heat of reaction  11.4. Specific heat capacity and calorimetry  11.5. Energy Changes in Combustion Reactions
  12. Electrochemistry  12.1. Electrolytes and non-electrolytes  12.2. Electrolysis and its applications (electroplating, extraction of metals)  12.3. Redox reactions (oxidation and reduction)  12.4. Galvanic cell and electrochemical series  12.5. Corrosion and electrochemical prevention methods
  13. Chemical kinetics and equilibrium  13.1. Rate of chemical reactions and its measurement  13.2. Factors affecting the reaction rate (catalyst, temperature, concentration)  13.3. Reversible and irreversible reactions  13.4. Dynamic equilibrium and equilibrium constant  13.5. Le Chatelier's principle and its applications
  14. Gases and Gas Laws  14.1. Properties of gases and kinetic molecular theory  14.2. Boyle's Law (Pressure-Volume Relation)  14.3. Charles's Law  14.4. Gay-Lussac's Law  14.5. Combined Gas Law and Ideal Gas Law  14.6. Real Gases vs Ideal Gases
  15. Nuclear Chemistry  15.1. Introduction to Radioactivity and Nuclear Reactions  15.2. Types of radioactive decay (alpha, beta, gamma)  15.3. Half-life and applications of radioactive isotopes  15.4. Nuclear fission and fusion reactions  15.5. Nuclear power generation and its environmental impact

Grade 10 → Stoichiometry and Chemical Calculations ↓


Stoichiometric calculations and chemical yield


Stoichiometry is a branch of chemistry that deals with the relative amounts of reactants and products in a chemical reaction. It involves calculations that estimate the amounts of substances consumed and produced in a reaction. One of the main parts of stoichiometry is understanding how stoichiometric calculations are performed and how these relate to chemical yield, which is the amount of product obtained in a chemical reaction.

Basic concepts of stoichiometry

Stoichiometry is based on the conservation of mass, where the total mass of the reactants is equal to the total mass of the products. The key is to add the reactants and products quantitatively using a balanced chemical equation. This includes:

  • Understanding the mole concept and Avogadro's number.
  • Using molar mass to convert between grams and moles.
  • Using the coefficients in balanced equations to determine mole ratios.

Example 1: Balancing a chemical equation

Consider the combustion reaction of propane:

C 3 H 8 + O 2 → CO 2 + H 2 O

First, balance the equation:

  1. Balance the carbon atoms:
    C 3 H 8 + O 2 → 3 CO 2 + H 2 O
  2. Balance the hydrogen atoms:
    C 3 H 8 + O 2 → 3CO 2 + 4H 2 O
  3. Balance the oxygen atoms:
    C 3 H 8 + 5 O 2 → 3CO 2 + 4H 2 O

The balanced equation is:

C 3 H 8 + 5O 2 → 3CO 2 + 4H 2 O

Stoichiometric calculations

Stoichiometric calculations usually involve determining the mass of one substance in a chemical equation given the mass of another substance. Here's how to do it:

Very basic stoichiometry steps

  1. Convert a given mass of a substance into moles using its molar mass.
  2. Use the stoichiometric coefficients (mole ratios) from the balanced equation to convert moles of one substance to moles of another.
  3. Convert moles back to grams if necessary.

Example 2: Simple stoichiometric calculation

Suppose you burn 11.0 g of propane (C 3 H 8 ). Find the mass of carbon dioxide produced.

1. Calculate the moles of C 3 H 8:

Molar mass of C 3 H 8 = 44.1 g/mol
Moles of C 3 H 8 = 11.0 g / 44.1 g/mol = 0.249 moles

2. Use the balanced equation to find the moles of CO2:

C 3 H 8 + 5O 2 → 3CO 2 + 4H 2 O
0.249 mol C 3 H 8 × (3 mol CO 2 / 1 mol C 3 H 8 ) = 0.747 mol CO 2

3. Convert moles of CO2 to grams:

Molar mass of CO2 = 44.0 g/mol
Mass of CO2 = 0.747 mol × 44.0 g/mol = 32.868 g

The mass of CO2 produced is about 32.87 grams.

Chemical byproducts

Chemical yield is the amount of product obtained in a chemical reaction. It is divided into two types:

  • Theoretical yield: The amount of product predicted by stoichiometry, based on a balanced chemical equation where the reaction proceeds completely to completion.
  • Actual yield: The amount of product actually obtained from a reaction.

The percent yield is then calculated to see how efficient the reaction was.

Percentage yield = (actual yield / theoretical yield) × 100

Example 3: Calculating chemical yield

Consider a reaction where the theoretical yield of a product is 20.0 g, but only 15.0 g of product is obtained experimentally.

Calculate the percentage yield:

Percent yield = (15.0 g / 20.0 g) × 100 = 75%

The percentage yield is 75%, which shows the efficiency of the process.

Visualization of stoichiometry through reactions

Let's imagine a simple reaction:

Water is formed by the reaction of hydrogen and oxygen:

2H 2 + O 2 → 2H 2 O

Visualize breaking and making bonds:

H2H2O2H2OH2O

The shape of each molecule, represented by a rectangular box, changes as bonds are broken and water is formed.

Conclusion

Understanding stoichiometric calculations and chemical yields are essential for predicting the outcomes of chemical reactions. Mastering these fundamental concepts is important for anyone studying chemistry.

By practicing with different chemical equations and scenarios, one can gain confidence in performing these calculations and understanding the relationship between reactants and products in any reaction. This will help in making accurate predictions about quantities in chemical experiments and industrial processes.

We hope this detailed explanation provides a solid understanding of stoichiometric calculations and chemical yield. Remember to take the time to practice these concepts with different chemical equations to further broaden your understanding.


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