Chemical reaction and equation notes class 10Class 10
Chemical reactions an equation notes class 10 are designed to understand various chemical reaction and equation concepts. Their are processes where substances undergo chemical changes to form new substances. They are essential for life, industry, and the environment.
Chemical reactions can be broadly classified into five types: combination reactions, decomposition reactions, displacement reactions, double displacement reactions, and redox reactions. In combination reactions, two or more substances combine to form a single substance. In decomposition reactions, a single substance breaks down into two or more simpler substances. In displacement reactions, an element displaces another element from a compound. In double displacement reactions, the cations and anions of two different compounds switch places. In redox reactions, there is a transfer of electrons between substances.
Understanding chemical reactions is important because they are responsible for the production of many essential products, such as food, medicine, and fuel. Additionally, chemical reactions play a significant role in environmental processes such as the water cycle and the carbon cycle. They also have practical applications in many industries, such as the production of plastics, fertilizers, and pharmaceuticals. By understanding the types of chemical reactions and their applications, we can develop new technologies and processes to improve our lives and the world around us.
A chemical equation is a symbolic representation of a chemical reaction in which the reactants and products are represented by their respective chemical formulas. It shows the starting materials, or reactants, on the left side of the equation and the resulting substances, or products, on the right side of the equation.
Chemical equations are important tools for scientists and chemists to communicate information about chemical reactions, such as the types and quantities of reactants and products involved. They also allow for the prediction of the outcome of a chemical reaction and the calculation of the amounts of reactants needed or products formed
Balancing Chemical Equations
Balancing chemical equations involves adjusting the coefficients of the reactants and products to ensure that the law of conservation of mass is satisfied. This law states that in any chemical reaction, the total mass of the reactants must be equal to the total mass of the products.
To balance a chemical equation, one must first write the chemical formulas of the reactants and products, and then adjust the coefficients until the number of atoms of each element is equal on both sides of the equation.
Balancing chemical equations is important because it ensures that the amounts of reactants and products are accurately represented in the equation. This information is essential for predicting the yield of a reaction, calculating the amount of reactants needed, and understanding the fundamental properties of matter.
Law of Conservation of Mass
The Law of Conservation of Mass is a fundamental principle in chemistry that states that the total mass of the reactants in a chemical reaction must be equal to the total mass of the products. In other words, matter cannot be created or destroyed in a chemical reaction.
This means that the number of atoms of each element on the reactant side of a chemical equation must be equal to the number of atoms of each element on the product side of the equation. If the equation is not balanced, it means that the law of conservation of mass is not being satisfied.
The Law of Conservation of Mass is important because it allows scientists and chemists to predict the outcome of a chemical reaction and ensure that the amounts of reactants and products are accurately represented in a chemical equation. It also helps to illustrate the stoichiometry of a reaction, which is the quantitative relationship between reactants and products in a chemical reaction.
By understanding the Law of Conservation of Mass, scientists and chemists can design and optimize chemical processes, develop new materials, and study the fundamental properties of matter. This knowledge is essential for advancing our understanding of chemistry and developing new technologies and processes to improve our lives and the world around us.
Steps for Balancing Chemical Equations
Balancing a chemical equation involves adjusting the coefficients of the reactants and products to ensure that the law of conservation of mass is satisfied. Here are the steps for balancing a chemical equation:
Write the unbalanced equation: Start by writing the chemical equation for the reaction, with the reactants on the left side and the products on the right side.
Count the atoms: Count the number of atoms of each element on both sides of the equation.
Choose a starting element: Choose an element that appears in more than one compound in the equation as a starting point for balancing.
Add coefficients: Add coefficients to the compounds on one side of the equation to balance the number of atoms of the starting element on both sides of the equation.
Repeat for other elements: Repeat steps 3 and 4 for other elements until all elements are balanced.
Check the balance: Check that the number of atoms of each element is the same on both sides of the equation. If not, adjust the coefficients until the equation is balanced.
Check the whole equation: Finally, check that the equation is balanced as a whole by verifying that the total number of atoms of each element is the same on both sides of the equation.
By following these steps, scientists and chemists can balance chemical equations accurately, ensuring that the law of conservation of mass is satisfied and that the amounts of reactants and products are accurately represented in the equation.
To Make Equations More Informative:
Writing the symbols of physical states of substances in a chemical equation:
By writing the physical states of substances, a chemical equation becomes more informative.
- Gaseous state is represented by symbol (g).
- Liquid state is represented by symbol (l).
- Solid state is written by symbol (s).
- Aqueous solution is written by symbol (aq).
- Writing the condition in which reaction takes place: The condition is generally written above and/or below the arrow of a chemical equation.
Thus, by writing the symbols of the physical state of substances and condition under which reaction takes place, a chemical equation can be made more informative.
Types of Chemical Equations
There are several types of chemical equations that scientists and chemists use to represent different types of chemical reactions. Here are some of the most common types of chemical equations:
Combination or Synthesis Reactions: These reactions occur when two or more reactants combine to form a single product. The general form of a combination reaction can be represented as A + B → AB.
Eg. Mg(s) + O2(g) → 2MgO(s)
Magnesium + Oxygen → Magnesium Oxide
Decomposition Reactions: These reactions occur when a single reactant breaks down into two or more products. The general form of a decomposition reaction can be represented as AB → A + B.
When calcium carbonate is heated, it decomposes into calcium oxide and carbon dioxide.
CaCO3(s) heat−→− CaO(s) + CO2(g)
Calcium carbonate → Calcium oxide + Carbon dioxide
Thermal Decomposition:The decomposition of a substance on heating is known as Thermal Decomposition.
Example: 2Pb(NO3)2(s) heat−→− 2PbO(s) + 4NO2(g) + O2(g)
Electrolytic Decomposition: Reactions in which compounds decompose into simpler compounds because of passing of electricity, are known as Electrolytic Decomposition. This is also known as Electrolysis.
Example: When electricity is passed in water, it decomposes into hydrogen and oxygen.
Photolysis or Photo Decomposition Reaction: Reactions in which a compound decomposes because of sunlight are known as Photolysis or Photo Decomposition Reaction.
Example: When silver chloride is put in sunlight, it decomposes into silver metal and chlorine gas.
Single Displacement or Substitution Reactions: These reactions occur when one element is replaced by another element in a compound. The general form of a single displacement reaction can be represented as A + BC → B + AC.
When zinc reacts with hydrochloric acid, it gives hydrogen gas and zinc chloride.
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
Double Displacement or Metathesis Reactions: These reactions occur when two ionic compounds exchange ions to form two new compounds. The general form of a double displacement reaction can be represented as AB + CD → AD + CB.
When the solution of barium chloride reacts with the solution of sodium sulphate, white precipitate of barium sulphate is formed along with sodium chloride.
BaCl2(aq) + Na2SO4(aq) → BaSO4(s) (Precipitate) + 2NaCl(aq)
Precipitation Reaction: The reaction in which precipitate is formed by the mixing of the aqueous solution of two salts is called Precipitation Reaction.
Example: AgNO3(aqueous) + KCl(aqueous) —–AgCl(precipitate) + KNO3(aqueous)
Neutralization Reaction: The reaction in which an acid reacts with a base to form salt and water by an exchange of ions is called Neutralization Reaction.
Acid-Base Reactions: These reactions occur when an acid and a base react to form a salt and water. The general form of an acid-base reaction can be represented as acid + base → salt + water.
Redox Reactions: These reactions involve the transfer of electrons between reactants. Oxidation is the loss of electrons, while reduction is the gain of electrons. The general form of a redox reaction can be represented as
A redox reaction occurs when the oxidation states of the substrate change. The loss of electrons or an increase in the oxidation state of a chemical or its atoms is referred to as oxidation. The gain of electrons or a decrease in the oxidation state of a chemical or its atoms is referred to as reduction.
Oxidation and reduction take place simultaneously.
Oxidation: Substance loses electrons or gains oxygen or loses hydrogen.
Reduction: Substance gains electrons or loses oxygen or gains hydrogen.
Oxidising agent – a substance that oxidises another substance and self-gets reduced.
Reducing agent – a substance that reduces another substance and self-gets oxidised.
A + B → A+ + B- or A- + B → A + B+.
Understanding the different types of chemical equations is important for predicting the outcome of a chemical reaction and designing chemical processes. By using these equations, scientists and chemists can better understand the fundamental properties of matter and develop new technologies and processes to improve our lives and the world around us.
Endothermic and exothermic reaction
Exothermic reaction – heat is evolved during a reaction. Most of the combination reactions are exothermic.
Al + Fe2O3 → Al2O3 + Fe + heat
CH4 + 2O2 → CO2 + 2H2O + heat
Effect of oxidation reaction in everyday life
Endothermic – Heat is required to carry out the reaction.
6CO2 + 6H2O + Sunlight → C6H12O6 + 6O2
Most of the decomposition reactions are endothermic.
Gradual deterioration of a material, usually a metal, by the action of moisture, air or chemicals in the surrounding environment.
4Fe(s) + 3O2(from air) + xH2O(moisture) → 2Fe2O3.xH2O(rust)
Corrosion of copper:
Cu(s) + H2O(moisture) + CO2(from air) → CuCO3.Cu(OH)2(green)
Corrosion of silver:
Ag(s) + H2S (from air) → Ag2S(black) + H2(g)
It refers to the oxidation of fats and oils in food that is kept for a long time. It gives foul smell and bad taste to food. Rancid food causes stomach infection on consumption.
(i) Use of air-tight containers
(ii) Packaging with nitrogen
(iv) Addition of antioxidants or preservatives
Factors Affecting Chemical Reactions
Chemical reactions can be affected by a variety of factors that influence the rate and outcome of the reaction. Here are some of the most important factors that affect chemical reactions:
Temperature: Increasing the temperature generally increases the rate of a chemical reaction because it increases the kinetic energy of the molecules, which leads to more collisions between reactant molecules and greater chance of successful collisions.
Concentration of Reactants: Increasing the concentration of reactants increases the rate of the reaction by increasing the number of collisions between reactant molecules.
Surface Area: Increasing the surface area of solid reactants increases the rate of the reaction by exposing more of the reactant to the other reactant or catalyst.
Catalysts: Catalysts are substances that speed up a chemical reaction without being consumed in the reaction. They work by providing an alternative pathway for the reaction with lower activation energy, thus increasing the rate of the reaction.
Light: Some chemical reactions are sensitive to light, and exposure to light can increase or decrease the rate of the reaction.
Pressure: Increasing the pressure of gases generally increases the rate of the reaction because it increases the frequency of collisions between gas molecules.
Presence of other substances: The presence of impurities, contaminants, or other substances in the reaction mixture can affect the rate and outcome of the reaction.
Understanding the factors that affect chemical reactions is important for designing and optimizing chemical processes, predicting the outcome of a reaction, and developing new technologies and materials. By controlling these factors, scientists and chemists can improve the efficiency, safety, and sustainability of chemical reactions.
Applications of Chemical Reactions
Industrial Processes: Chemical reactions are used in various industrial processes to produce a wide range of products, such as fertilizers, plastics, pharmaceuticals, and fuels.
Energy Production: Chemical reactions are used to generate energy, such as in the combustion of fossil fuels to produce heat and electricity, or in the production of biofuels from renewable sources.
Food and Beverage Production: Chemical reactions are used in the production of food and beverages, such as fermentation in the production of beer, wine, and cheese, or in the baking of bread and pastries.
Environmental Cleanup: Chemical reactions are used in environmental cleanup to break down pollutants and contaminants, such as in the bioremediation of oil spills or the treatment of wastewater.
Medical and Healthcare: Chemical reactions are used in various medical and healthcare applications, such as in the synthesis of pharmaceuticals, the diagnosis of diseases through biochemical tests, and the sterilization of medical equipment.
Agriculture: Chemical reactions are used in agriculture to produce fertilizers and pesticides, as well as in the genetic modification of crops to improve their yield, resistance to pests, and nutritional content.
Household Products: Chemical reactions are used in various household products, such as cleaning agents, detergents, and personal care products.
Understanding the applications of chemical reactions is important for developing new technologies and materials that can improve our lives and the world around us. By harnessing the power of chemical reactions, scientists and engineers can create innovative solutions to some of the biggest challenges facing society today.