Chemical Reactions PDF

Created by Turbolearn AI Chemical Changes and Reactions Chemical changes occur when the chemical nature of a substance is altered, resulting in a new substance with different properties. Examples of chemical changes include milk turning sour, iron rusting, and grapes fermenting to produce alcohol....

Created by Turbolearn AI Chemical Changes and Reactions Chemical changes occur when the chemical nature of a substance is altered, resulting in a new substance with different properties. Examples of chemical changes include milk turning sour, iron rusting, and grapes fermenting to produce alcohol. Characteristics of Chemical Reactions Chemical reactions are characterized by: Change in state Change in color Evolution of gas Change in temperature Change in chemical nature of the initial substance These observations help identify a chemical reaction. Chemical Equations A chemical equation is a representation of a chemical reaction using symbols and formulas. It consists of reactants (starting materials) and products (resulting substances) separated by an arrow. A chemical equation is a concise way to represent a chemical reaction, showing the reactants, products, and direction of the reaction. The general format of a chemical equation is: Reactants → Products For example, the reaction between magnesium and oxygen can be represented as: Magnesium + Oxygen → Magnesium Oxide Using chemical formulas, this equation becomes: Mg + O2 → MgO However, this equation is not balanced, as the number of atoms on the left and right sides is not equal. Balancing Chemical Equations Page 1  Created by Turbolearn AI To balance a chemical equation, we need to ensure that the number of atoms of each element is the same on both the reactant and product sides. This is based on the Law of Conservation of Mass, which states that atoms are neither created nor destroyed in a chemical reaction. The steps to balance a chemical equation are: 1. Write the unbalanced equation 2. Count the number of atoms of each element on both sides 3. Adjust the coefficients (numbers in front of the formulas) to balance the equation For example, consider the reaction: Fe + H2O → Fe3O4 + H2 To balance this equation, we need to adjust the coefficients: Element Reactants Products Fe 1 3 H 2 2 O 1 4 By adjusting the coefficients, we get: 3Fe + 4H2O → Fe3O4 + 4H2 This equation is now balanced. Physical States and Reaction Conditions The physical states of reactants and products can be indicated using the following notations: G: Gas L: Liquid AQ: Aqueous (solution in water) S: Solid Reaction conditions, such as temperature, pressure, and catalysts, can be indicated above or below the arrow in the equation. For example: CO (G) + 2H2 (G) → CH3OH (L) (at 340 ATM) Page 2  Created by Turbolearn AI Examples and Practice Consider the reaction: Hydrogen + Chlorine → Hydrogen Chloride The unbalanced equation is: H2 + Cl2 → HCl To balance this equation, we need to adjust the coefficients: Element Reactants Products H 2 1 Cl 2 1 By adjusting the coefficients, we get: H2 + Cl2 → 2HCl This equation is now balanced.## Balancing Chemical Equations To balance a chemical equation, the number of atoms of each element must be the same on both the reactant and product sides. For example, in the reaction between hydrogen gas and chlorine gas to produce hydrogen chloride gas, we need to balance the number of atoms of hydrogen and chlorine. Element Reactant Side Product Side Hydrogen 2 2 Chlorine 2 2 To balance the equation, we need two molecules of HCl on the product side. Writing Balanced Equations The steps to write a balanced equation are: Write the unbalanced equation with reactants and products Identify the number of atoms of each element on both sides of the equation Balance the atoms by adding coefficients in front of the formulas of reactants or products For example, in the reaction between barium chloride and aluminum sulfate to produce barium sulfate and aluminum chloride, we can tabulate the number of atoms of each element as follows: Page 3  Created by Turbolearn AI Element Reactant Side Product Side Barium 1 1 Chlorine 2 3 Aluminum 2 1 Sulfate 3 1 To balance the equation, we need to add coefficients in front of the formulas of reactants or products. Types of Chemical Reactions There are several types of chemical reactions, including: Combination Reactions: a type of chemical reaction where two or more reactants combine to form a single product Decomposition Reactions: a type of chemical reaction in which a single compound breaks down into two or more simpler substances Displacement Reactions: a type of chemical reaction where one element displaces another element from a compound Double Displacement Reactions: a type of chemical reaction where two compounds react by exchanging ions to form two new compounds Combination Reactions A combination reaction is a type of chemical reaction where two or more reactants combine to form a single product. Examples of combination reactions include: Burning of coal: carbon + oxygen → carbon dioxide Formation of water: hydrogen + oxygen → water Decomposition Reactions A decomposition reaction is a type of chemical reaction in which a single compound breaks down into two or more simpler substances. Examples of decomposition reactions include: Page 4  Created by Turbolearn AI Thermal decomposition of ferrous sulfate: ferrous sulfate → ferric oxide + sulfur dioxide + sulfur trioxide Thermal decomposition of calcium carbonate: calcium carbonate → calcium oxide + carbon dioxide Displacement Reactions A displacement reaction is a type of chemical reaction where one element displaces another element from a compound. Examples of displacement reactions include: Iron + copper sulfate → iron sulfate + copper Zinc + copper sulfate → zinc sulfate + copper Double Displacement Reactions A double displacement reaction is a type of chemical reaction where two compounds react by exchanging ions to form two new compounds. Examples of double displacement reactions include: Sodium sulfate + barium chloride → barium sulfate + sodium chloride Oxidation and Reduction Reactions An oxidation reaction is a type of chemical reaction where a substance gains oxygen. Examples of oxidation reactions include: Copper + oxygen → copper(II) oxide A reduction reaction is a type of chemical reaction where a substance loses oxygen. Some chemical reactions are exothermic, meaning they release heat, while others are endothermic, meaning they absorb heat. Examples of exothermic reactions include: Burning of natural gas: methane + oxygen → carbon dioxide + water + heat Cellular respiration: glucose + oxygen → carbon dioxide + water + energy Examples of endothermic reactions include: Page 5  Created by Turbolearn AI Decomposition of calcium carbonate: calcium carbonate → calcium oxide + carbon dioxide Electrolysis of water: water → hydrogen + oxygen## Reduction Reactions A reduction reaction occurs when a substance loses oxygen during a reaction. For example, when hydrogen gas is passed over heated copper oxide, the black surface coating undergoes a transformation, turning brown as the reverse reaction occurs, and finally copper is obtained. Oxidation-Reduction Reactions This reaction has both oxidation and reduction in it. A reaction in which one reactant gets oxidized while the other gets reduced is called an oxidation-reduction reaction or simply a redox reaction. In the case of copper oxide turning to copper, it is a reduction reaction, whereas hydrogen turning to water is an oxidation reaction. During this reaction, copper oxide gets reduced by losing oxygen, and hydrogen is gaining oxygen and is being oxidized. Examples of Redox Reactions Some other examples of redox reactions include: Zinc oxide plus carbon gives rise to zinc plus carbon monoxide Manganese oxide plus 4HCL gives rise to manganese chloride plus 2H2O plus Cl2 Effects of Oxidation Reactions The effects of oxidation reactions can be seen in our day-to-day life, including: Corrosion: when a metal is affected by substances around it, such as moisture, acids, etc. Rusting of iron: when iron is exposed to moisture, it gets coated with a reddish-brown powder Rancidity: when fats and oils are exposed to air, they get oxidized, leading to a change in their smell and taste Prevention of Oxidation Page 6  Created by Turbolearn AI To prevent the oxidation of fatty foods, the following preventive steps are followed: Adding antioxidant chemicals to the foods Keeping food in a tight container Filling the chips packets with nitrogen gas Summary of Redox Reactions The following table summarizes the key points about redox reactions: Reaction Example Description Copper oxide to Reduction Loss of oxygen Copper Oxidation Hydrogen to Water Gain of oxygen Zinc oxide plus One reactant gets oxidized, the other gets Redox Carbon reduced window.MathJax = { tex: { inlineMath: [['$', '$'], ['\\(', '\\)']], displayMath: [['$$', '$$'], ['\\[', '\\]']] } }; Page 7