Chemical Reactions and Equations Chapter 1
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Questions and Answers

What are some observations that can help determine whether a chemical reaction has taken place?

change in state, change in colour, evolution of a gas, change in temperature

Which of the following is a product of burning a magnesium ribbon?

  • Magnesium chloride
  • Magnesium oxide (correct)
  • Magnesium sulfate
  • Magnesium hydroxide

    • The chemical equation for the reaction when zinc reacts with sulfuric acid is: Zinc + Sulfuric acid → Zinc ____ + Hydrogen.

    sulfate

    Balanced chemical equations follow the law of conservation of mass.

    <p>True</p> Signup and view all the answers

    Why should a magnesium ribbon be cleaned before burning in air?

    <p>To remove any oxide layer or impurities on the surface</p> Signup and view all the answers

    Write the balanced equation for the chemical reaction: Hydrogen + Chlorine → Hydrogen chloride

    <p>H2 + Cl2 → 2HCl</p> Signup and view all the answers

    Write the balanced equation for the chemical reaction: Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride

    <p>3BaCl2 + Al2(SO4)3 → 3BaSO4 + 2AlCl3</p> Signup and view all the answers

    Write the balanced equation for the chemical reaction: Sodium + Water → Sodium hydroxide + Hydrogen

    <p>2Na + 2H2O → 2NaOH + H2</p> Signup and view all the answers

    Write a balanced chemical equation with state symbols for the reaction: Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.

    <p>BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)</p> Signup and view all the answers

    Write a balanced chemical equation with state symbols for the reaction: Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

    <p>NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)</p> Signup and view all the answers

    What form of energy is causing the decomposition reactions of 2AgBr(s) and 2AgCl(s) in black and white photography?

    <p>Sunlight</p> Signup and view all the answers

    In the reaction Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s), what color change is observed and why?

    <p>Iron nail becomes brownish and the blue color of copper sulphate solution fades. This is because iron displaces copper in the solution, causing the color change.</p> Signup and view all the answers

    What is the white substance formed in the double displacement reaction Na2SO4(aq) + BaCl2(aq) → BaSO4(s) + 2NaCl(aq)?

    <p>BaSO4 (Barium sulfate)</p> Signup and view all the answers

    Which of the following statements about oxidation and reduction reactions are true?

    <p>If a substance gains oxygen, it is oxidised.</p> Signup and view all the answers

    What is the process called when a metal is attacked by substances like moisture or acids, resulting in damage?

    <p>Corrosion</p> Signup and view all the answers

    Which of the statements about the reaction below are incorrect? 2PbO(s) + C(s) → 2Pb(s) + CO2(g)

    <p>Carbon is getting oxidised.</p> Signup and view all the answers

    Fe2O3 + 2Al → Al2O3 + 2Fe. The above reaction is an example of a

    <p>displacement reaction.</p> Signup and view all the answers

    What happens when dilute hydrochloric acid is added to iron fillings?

    <p>Hydrogen gas and iron chloride are produced.</p> Signup and view all the answers

    What is a balanced chemical equation? Why should chemical equations be balanced?

    <p>A balanced chemical equation has an equal number of atoms for each element on both sides. Chemical equations should be balanced to obey the law of conservation of mass.</p> Signup and view all the answers

    Translate the following statements into chemical equations and then balance them:

    <p>Answers may vary.</p> Signup and view all the answers

    What does one mean by exothermic and endothermic reactions? Give examples.

    <p>Exothermic reactions release heat and energy to the surroundings, while endothermic reactions absorb heat and energy from the surroundings. Example of exothermic reaction: Combustion. Example of endothermic reaction: Photosynthesis.</p> Signup and view all the answers

    Why is respiration considered an exothermic reaction? Explain.

    <p>Respiration is exothermic because it releases energy in the form of heat and is a process of breaking down glucose to produce energy needed for cell functions.</p> Signup and view all the answers

    Why do we apply paint on iron articles?

    <p>To prevent rusting and corrosion of iron articles by creating a barrier that prevents exposure to moisture and oxygen.</p> Signup and view all the answers

    Oil and fat containing food items are flushed with nitrogen. Why?

    <p>To prevent oxidation and rancidity of oil and fat by displacing the oxygen in the air which can lead to the degradation of the oil or fat.</p> Signup and view all the answers

    What do you mean by a precipitation reaction? Explain by giving examples.

    <p>A precipitation reaction is when two soluble salts react to form an insoluble solid, known as a precipitate. Example: AgNO3 + NaCl → AgCl ↓ + NaNO3.</p> Signup and view all the answers

    Study Notes

    Chemical Reactions and Equations

    Chemical reactions are an essential aspect of our daily lives, playing a crucial role in various industries and processes. Chemical reactions involve the transformation of one or more substances into new substances, resulting in a change in the chemical composition of the original substances.

    Chemical reactions can occur spontaneously or be triggered by various factors such as temperature, pressure, light, or catalysts. Understanding chemical reactions is vital in various fields such as medicine, agriculture, and environmental protection.

    Chemical Equations

    A chemical equation is a symbolic representation of a chemical reaction, using chemical formulas and symbols to represent the reactants, products, and their physical states. Chemical equations provide a concise and efficient way to describe complex chemical reactions. A word-equation is a descriptive representation of a chemical reaction in sentence form.

    For instance, the reaction between magnesium and oxygen can be written as follows:

    Mg + O2 → MgO

    In this equation, magnesium (Mg) reacts with oxygen (O2) to form magnesium oxide (MgO). The arrowhead points towards the products, indicating the direction of the reaction.

    Writing a Chemical Equation

    A chemical equation can be written in a shorter form using chemical formulae, making it easier to understand and analyze complex reactions. The reactants are written on the left-hand side (LHS) with a plus sign (+) between them, while the products are written on the right-hand side (RHS) with another plus sign (+) between them. The arrowhead points towards the products, indicating the direction of the reaction.

    Balancing Chemical Equations

    Balancing chemical equations is a critical step in chemical reaction analysis. A balanced equation is one where the number of atoms of each element is the same on both the reactant and product sides. The law of conservation of mass states that mass cannot be created or destroyed in a chemical reaction. To balance an equation, one can start by counting the number of atoms of each element on both sides of the equation, then use coefficients to balance the equation while following the rules of balancing.

    Types of Chemical Reactions

    There are several types of chemical reactions, including combination reactions, decomposition reactions, exothermic reactions, and many others.

    • Combination reactions: In this type of reaction, two or more substances combine to form a single product.
    • Decomposition reactions: In this type of reaction, a single reactant breaks down into simpler products.

    Exothermic Reactions

    Exothermic reactions are chemical reactions that release heat along with the formation of products. These reactions are often accompanied by a release of heat, which can be beneficial in various industrial processes.

    Thermal Decomposition Reactions

    Thermal decomposition reactions involve the breakdown of reactants when heated. These reactions often require energy to initiate the decomposition process, which can be provided in the form of heat, light, or electricity.

    Electrolysis of Water

    Electrolysis of water involves the decomposition of water into hydrogen and oxygen gases. This process is often used in various industrial applications and is an essential step in the production of various chemicals.

    Displacement Reactions

    Displacement reactions involve the replacement of one element by another in a compound. These reactions are often used in various industrial processes, such as the extraction of metals from ores.

    <h3(Double Displacement Reactions

    Double displacement reactions involve the exchange of partners between two compounds, resulting in the formation of two new compounds. These reactions often produce a precipitate and are used in various industrial applications.

    Oxidation and Reduction

    Oxidation is the gain of oxygen or loss of hydrogen, while reduction is the loss of oxygen or gain of hydrogen. Oxidation and reduction reactions are essential in various biological and industrial processes.

    Corrosion

    Corrosion is the process of metal degradation due to reaction with the environment. Corrosion can occur through various means, including moisture, oxygen, and other environmental factors.

    Rancidity

    Rancidity is the process of oxidation of fats and oils, leading to a change in taste and smell. Rancidity can be caused by various factors, including heat, light, and oxygen.

    Importance of Balanced Equations

    Balanced chemical equations are essential for understanding chemical reactions and making predictions about the outcome of a chemical reaction. Balancing chemical equations represents the reactants, products, and their physical states symbolically. Chemical equations must be balanced to ensure that the number of atoms of each type involved in the reaction is the same on the reactant and product sides. Balanced equations are critical for

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    Explore the basics of chemical reactions and equations through everyday examples, including milk spoilage, iron corrosion, fermentation, cooking, and digestion.

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