Chemical Reactions and Equations Chapter 1

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Questions and Answers

What is the main reason for balancing a chemical equation?

  • To study the properties of elements
  • To follow the law of multiple proportions
  • To satisfy the law of conservation of mass (correct)
  • To obey the law of definite proportions

What type of chemical equation is Equation (1.2) according to the text?

  • A chemical reaction
  • A skeletal chemical equation (correct)
  • A balanced chemical equation
  • A word-equation

What is the purpose of drawing boxes around each formula in a chemical equation?

  • To satisfy the law of conservation of mass
  • To balance the chemical equation (correct)
  • To write the word-equation
  • To identify the reactants and products

Which element has the same number of atoms on both sides of the arrow in Equation (1.3)?

<p>All of the above (D)</p> Signup and view all the answers

What is the result of not balancing a chemical equation?

<p>The mass is not conserved (B)</p> Signup and view all the answers

What is the purpose of balancing a chemical equation?

<p>To ensure the conservation of mass (C)</p> Signup and view all the answers

What is the characteristic of a balanced chemical equation?

<p>The number of atoms of each element is the same on both sides (D)</p> Signup and view all the answers

What is the difference between a word-equation and a chemical equation?

<p>A word-equation is a sentence, while a chemical equation is a symbolic representation (C)</p> Signup and view all the answers

What is the purpose of rubbing the iron nails with sandpaper in Activity 1.9?

<p>To clean the iron nails and remove any impurities (C)</p> Signup and view all the answers

What is the function of the thread in Activity 1.9?

<p>To tie the two iron nails together (B)</p> Signup and view all the answers

What is observed in the copper sulphate solution in test tube B after 20 minutes?

<p>The intensity of the blue colour decreases (A)</p> Signup and view all the answers

What is the purpose of keeping one iron nail aside in Activity 1.9?

<p>To compare the colour of the iron nails (A)</p> Signup and view all the answers

What is the duration of time for which the iron nails are immersed in the copper sulphate solution in test tube B?

<p>20 minutes (C)</p> Signup and view all the answers

What is the volume of the copper sulphate solution taken in each test tube?

<p>10 mL (D)</p> Signup and view all the answers

What is compared in the copper sulphate solutions in test tubes A and B?

<p>The intensity of the blue colour (D)</p> Signup and view all the answers

What is the name of the reaction that occurs in Activity 1.9?

<p>Displacement Reaction (D)</p> Signup and view all the answers

What is the end result of burning a magnesium ribbon in air?

<p>Magnesium oxide (B)</p> Signup and view all the answers

What is the purpose of wearing eye protection in Activity 1.1?

<p>To protect the eyes from the white flame (A)</p> Signup and view all the answers

What is the primary reason for cleaning the magnesium ribbon with sandpaper?

<p>To remove impurities from the surface (C)</p> Signup and view all the answers

What is a common characteristic of all the situations mentioned in the introduction?

<p>They all involve chemical changes (C)</p> Signup and view all the answers

What is the term used to describe the process of milk turning sour when left at room temperature during summers?

<p>Fermentation (D)</p> Signup and view all the answers

What is the purpose of collecting the ash in a watch-glass in Activity 1.1?

<p>To collect the product of the chemical reaction (A)</p> Signup and view all the answers

What is the term used to describe the process of grapes turning into wine?

<p>Fermentation (A)</p> Signup and view all the answers

Why is it necessary to perform Activity 1.1 under the teacher's supervision?

<p>Because it involves handling hazardous materials (A)</p> Signup and view all the answers

What is the result of oxidation of copper?

<p>Copper oxide (C)</p> Signup and view all the answers

What happens to the copper(II) oxide during the reaction with hydrogen gas?

<p>It loses oxygen (B)</p> Signup and view all the answers

What is the definition of oxidation?

<p>Gain of oxygen or loss of hydrogen (B)</p> Signup and view all the answers

In reaction (1.31), what is the product of the oxidation of carbon?

<p>CO (A)</p> Signup and view all the answers

What is the type of reaction that occurs between copper oxide and hydrogen gas?

<p>Oxidation-reduction reaction (A)</p> Signup and view all the answers

What is the result of the reduction of zinc oxide?

<p>Zn (C)</p> Signup and view all the answers

What happens to the hydrogen during the reaction with copper oxide?

<p>It is oxidized to water (C)</p> Signup and view all the answers

What is the definition of reduction?

<p>Loss of oxygen or gain of hydrogen (A)</p> Signup and view all the answers

In the reaction 2Fe2O3 + 2Al → Al2O3 + 2Fe, which of the following is true?

<p>Iron is getting reduced. (C)</p> Signup and view all the answers

What is the result of adding dilute hydrochloric acid to iron fillings?

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

What is the purpose of a balanced chemical equation?

<p>To ensure that the number of atoms of each element is the same on both sides. (C)</p> Signup and view all the answers

What is the correct balanced equation for the reaction of hydrogen gas with nitrogen to form ammonia?

<p>3H2 + N2 → 2NH3 (B)</p> Signup and view all the answers

What is the type of reaction that occurs between barium chloride and aluminium sulphate?

<p>Double displacement reaction. (B)</p> Signup and view all the answers

What is the correct balanced equation for the reaction of calcium hydroxide with carbon dioxide to form calcium carbonate and water?

<p>Ca(OH)2 + CO2 → CaCO3 + H2O (C)</p> Signup and view all the answers

What is the type of reaction that occurs between zinc and silver nitrate?

<p>Displacement reaction. (C)</p> Signup and view all the answers

What is the correct balanced equation for the reaction of barium chloride with potassium sulphate to form barium sulphate and potassium chloride?

<p>BaCl2 + K2SO4 → BaSO4 + 2KCl (A)</p> Signup and view all the answers

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Study Notes

Chemical Reactions and Equations

  • Chemical reactions involve a change in the nature and identity of the initial substance, resulting in a new product.
  • Examples of chemical reactions in daily life include:
    • Milk spoiling when left at room temperature
    • Iron rusting when exposed to humid air
    • Grapes fermenting
    • Food cooking
    • Digestion of food in the body
    • Respiration

Chemical Equations

  • A chemical equation is a representation of a chemical reaction using symbols and formulas.
  • A skeletal chemical equation is a basic representation of a chemical reaction that may not be balanced.
  • The law of conservation of mass states that mass cannot be created or destroyed in a chemical reaction, so the total mass of elements in the reactants must equal the total mass of elements in the products.
  • A balanced chemical equation is one in which the number of atoms of each element is the same on both sides of the equation.

Balancing Chemical Equations

  • To balance a chemical equation, first draw boxes around each formula.
  • Count the number of atoms of each element on both sides of the equation and adjust the coefficients as necessary to make the equation balanced.

Types of Chemical Reactions

  • Displacement reactions: a more reactive element displaces a less reactive element from a compound.
  • Oxidation-reduction reactions (redox reactions): one reactant is oxidized (loses electrons) while the other is reduced (gains electrons).
  • Examples of redox reactions include:
    • CuO + H2 → Cu + H2O
    • ZnO + C → Zn + CO
    • MnO2 + 4HCl → MnCl2 + 2H2O + Cl2

Characteristics of Chemical Reactions

  • If a substance gains oxygen during a reaction, it is said to be oxidized.
  • If a substance loses oxygen during a reaction, it is said to be reduced.
  • Oxidation and reduction occur simultaneously in a redox reaction.

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