Basic Concepts of Chemistry
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Questions and Answers

What is the term used to describe a measurement whose average value is close to the correct value?

  • Correct
  • Accurate (correct)
  • Precise
  • Concise
  • Which law states that matter can neither be created nor destroyed?

  • Gay Lussac's Law of combining volumes
  • Law of multiple proportions
  • Law of conservation of mass (correct)
  • Law of constant composition
  • What is the weight of sodium chloride decomposed by 4.9 g of sulphuric acid?

  • 6g
  • 5g
  • 3.2g (correct)
  • Cannot be determined
  • Which of the following is an example of the Law of Constant proportions?

    <p>Copper metal reacting with nitric acid</p> Signup and view all the answers

    What is the term used to describe a measurement whose values are close to each other and hence close to their average value?

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

    Which law states that a chemical compound is always found to be made up of the same elements combined together in the same fixed proportion by mass?

    <p>Law of constant composition or Definite Proportions</p> Signup and view all the answers

    When 4.2 g NaHCO3 is added to a solution of CH3COOH weighing 10g, what is the total mass of the products?

    <p>12.0 g</p> Signup and view all the answers

    What is the term used to describe the fixed ratio in which elements combine to form compounds?

    <p>Law of definite proportions</p> Signup and view all the answers

    What is the law of constant proportion?

    <p>The ratio of masses of elements in a compound is always constant.</p> Signup and view all the answers

    What is the law of multiple proportions?

    <p>When two elements combine to form two or more chemical compounds, the masses of one of the elements that combine with a fixed mass of the other bear a simple ratio to one another.</p> Signup and view all the answers

    In the experiment where 45g of metal M reacts with 40g of oxygen to produce a stable oxide, what can be concluded about the metal oxide formed?

    <p>The mass of metal oxide formed cannot be determined from the given information.</p> Signup and view all the answers

    What is the ratio of carbon content in the two oxides of carbon?

    <p>1.57:1</p> Signup and view all the answers

    What is the conclusion that can be drawn from the experiment where 3.45g of yellow oxide loses 0.24g on reduction?

    <p>The yellow oxide obeys the law of multiple proportions.</p> Signup and view all the answers

    What is the mass of metal required to produce 1190g of metal oxide?

    <p>45g × 1190g/40g</p> Signup and view all the answers

    What is the mass of metal oxide formed when 2.35g of oxygen is used in an experiment?

    <p>99.93g × 2.35g/86.55g</p> Signup and view all the answers

    What is the conclusion that can be drawn from the experiment where copper gives two oxides that produce 0.888g and 0.799g of metal on heating in hydrogen gas?

    <p>The two oxides have a simple whole-number ratio of copper content.</p> Signup and view all the answers

    Study Notes

    Accuracy and Precision

    • Accuracy refers to how close a measurement is to the true value
    • Precision refers to how close different measurements are to each other and their average value

    Laws of Chemical Combination

    • Law of Conservation of Mass: Matter cannot be created or destroyed, and the total mass of reactants is equal to the total mass of products
    • Law of Constant Composition or Definite Proportions: A chemical compound is always made up of the same elements combined in the same fixed proportion by mass
    • Law of Multiple Proportions: When two elements form two or more compounds, the masses of one element that combine with a fixed mass of the other bear a simple ratio to each other
    • Law of Reciprocal Proportions: Not mentioned in the provided text, but will be discussed later
    • Gay Lussac's Law of Combining Volumes: Not mentioned in the provided text, but will be discussed later

    Law of Conservation of Mass

    • Example 1: 4.2g NaHCO3 + 10g CH3COOH → 2.2g CO2 + 12.0g residue
    • Example 2: 4.9g H2SO4 + xg NaCl → 6g NaHSO4 + 1.825g HCl

    Law of Constant Composition

    • Example 1: 2.16g Cu → 2.70g CuO, and 1.15g CuO → 0.92g Cu
    • Example 2: 0.5g Ag → 0.66g AgCl, and 1g Ag → 1.32g AgCl
    • Example 3: 1.75g metal → 2.19g CuO, and 1.14g metal → 1.43g CuO
    • Example 4: 29.4g Mg → 49g MgO, and 5.9g Mg → 9.83g MgO
    • Example 5: 45g metal M → 1190g metal oxide, and 86.55g metal → 99.93g metal oxide

    Law of Multiple Proportions

    • Example 1: Carbon forms two oxides with 42.9% and 27.3% carbon respectively
    • Example 2: Lead forms two oxides, with 3.45g yellow oxide losing 0.24g on reduction, and 1.227g brown oxide losing 0.16g on reduction
    • Example 3: Copper forms two oxides, with 0.888g and 0.799g of metal produced on heating 1g of each oxide in hydrogen gas

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    This quiz covers fundamental concepts of chemistry including laws of chemical composition, stoichiometry, and chemical quantities such as molarity, normality, and molality.

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