Inorganic Chemistry: Archimedes' Principle
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Questions and Answers

What is the formula mass of baking soda (NaHCO3)?

  • 84 g/mol (correct)
  • 94 g/mol
  • 104 g/mol
  • 74 g/mol

    • What are cations?

  • Atoms that have gained electrons
  • Positively charged ions (correct)
  • Negatively charged ions
  • Neutrally charged atoms

    • To determine the formula mass of ammonium nitrate (NH4NO3), which of the following must be calculated?

  • The total mass of nitrogen, hydrogen, and oxygen (correct)
  • The mass of ammonium only
  • Only hydrogen and oxygen mass combined
  • The mass of only nitrogen and hydrogen

    • How are free radicals described in the context of chemical species?

    <p>Unstable atoms or molecules with unpaired electrons</p> Signup and view all the answers

    What typically happens to metal atoms in terms of charge?

    <p>They lose electrons to form cations</p> Signup and view all the answers

    What is the primary role of potassium chlorate (KClO3) in a laboratory setting?

    <p>To prepare oxygen gas</p> Signup and view all the answers

    What characterizes an ionic compound?

    <p>Contains both cations and anions that are electrically neutral</p> Signup and view all the answers

    What is the main action that results in the formation of anions?

    <p>Gaining electrons</p> Signup and view all the answers

    What is the molecular mass of glucose (C6H12O6)?

    <p>180.096 amu</p> Signup and view all the answers

    Which term is used specifically for molecular compounds?

    <p>Molecular mass</p> Signup and view all the answers

    What is the formula mass of sodium chloride (NaCl)?

    <p>58.5 amu</p> Signup and view all the answers

    What is the molecular mass of naphthalene (C10H8)?

    <p>128 amu</p> Signup and view all the answers

    Which formula represents the simplest ratio of cations and anions in an ionic compound?

    <p>Formula unit</p> Signup and view all the answers

    What is the relative atomic mass of hydrogen based on its mass as a percentage of a C-12 atom?

    <p>1.008 amu</p> Signup and view all the answers

    What is the empirical formula of glucose given the simplest ratio of C, H and O atoms is 1:2:1?

    <p>CH2O</p> Signup and view all the answers

    What is the formula mass of magnesium hydroxide (Mg(OH)2)?

    <p>74 amu</p> Signup and view all the answers

    Which of the following elements has a relative atomic mass closest to 15.9994 amu?

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

    Which statement is true about ionic compounds?

    <p>Ionic compounds consist of arrays of oppositely charged ions.</p> Signup and view all the answers

    When calculating molecular mass, what does the term 'subscript' refer to?

    <p>The number of specific atoms in a molecule</p> Signup and view all the answers

    If the molecular formula of hydrogen peroxide is H2O2, what is its empirical formula?

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

    What does the molecular formula of a compound indicate compared to the empirical formula?

    <p>It indicates the actual number of each atom in a molecule.</p> Signup and view all the answers

    Which element has the highest relative atomic mass among the following options?

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

    Which of the following formulas represents the relative atomic mass of Sodium?

    <p>22.9898 amu</p> Signup and view all the answers

    What is the simplest whole-number ratio of hydrogen to oxygen in water?

    <p>2:1</p> Signup and view all the answers

    What was Archimedes tasked with determining regarding the crown?

    <p>If it was made of pure gold or impure gold</p> Signup and view all the answers

    Which observation did Archimedes make while bathing that led to his discovery?

    <p>More water overflowed the bath tank</p> Signup and view all the answers

    What principle did Archimedes use to determine the purity of the crown?

    <p>The equal displacement of water by equal weights</p> Signup and view all the answers

    Which branch of chemistry deals with the substances that Archimedes was investigating?

    <p>Inorganic Chemistry</p> Signup and view all the answers

    What does the term 'Eureka' signify in Archimedes' discovery?

    <p>I have found it</p> Signup and view all the answers

    What physical sensation did Archimedes experience when submerged in water?

    <p>Loss of weight</p> Signup and view all the answers

    How did Archimedes plan to test the crown's purity?

    <p>By weighing it and observing the water displacement</p> Signup and view all the answers

    Which branch of chemistry focuses on the large-scale production of useful substances?

    <p>Industrial Chemistry</p> Signup and view all the answers

    What is the mass of hydrogen peroxide (H2O2) that would contain 2.5 moles?

    <p>85 grams</p> Signup and view all the answers

    How many moles of H2O2 are there in a 30g sample?

    <p>0.88 moles</p> Signup and view all the answers

    What is the number of moles in 12.5 grams of sodium chloride (NaCl)?

    <p>0.21 moles</p> Signup and view all the answers

    What is the mass of one mole of barium sulfate (BaSO4)?

    <p>233 grams</p> Signup and view all the answers

    How many atoms are present in 1.25 moles of zinc (Zn)?

    <p>7.53 x 10^23 atoms</p> Signup and view all the answers

    How many molecules are in 0.5 moles of methane (CH4)?

    <p>3.01 x 10^23 molecules</p> Signup and view all the answers

    How many atoms are present in 0.2 moles of aluminum (Al)?

    <p>3.21 x 10^23 atoms</p> Signup and view all the answers

    How many molecules are in 0.25 moles of sulfur dioxide (SO2)?

    <p>1.50 x 10^23 molecules</p> Signup and view all the answers

    Study Notes

    Archimedes' Contribution to Density Measurement

    • Tasked by the Greek emperor to determine the purity of a gold crown using carbonates, bicarbonates, and oxides.
    • The principle of buoyancy discovered while bathing led to the concept of displaced liquid volume.
    • Concluded that loss of weight when submerged in water equals the weight of the displaced liquid.
    • Designed an experiment to weigh the crown against pure gold: if densities matched, the crown was pure; if not, it was impure.
    • His famous exclamation "Eureka" signified his realization and discovery process.

    Branches of Chemistry

    • Inorganic Chemistry: Focuses on elements and compounds excluding organic compounds.
    • Biochemistry: Studies physical and chemical changes in living organisms.
    • Industrial Chemistry: Involves large-scale production of useful substances and methods using technology.

    Atomic Mass and Relative Atomic Mass

    • Mass of a C-12 atom is defined as 12 amu; hydrogen is 8.40% as massive as the C-12 atom.
    • Relative atomic mass of hydrogen calculated: 1.008 amu.
    • Relative atomic masses of key elements:
      • Oxygen (O): 15.9994 amu
      • Sodium (Na): 22.9898 amu
      • Aluminum (Al): 26.9815 amu
      • Iron (Fe): 55.847 amu
      • Chlorine (Cl): 35.453 amu
      • Nitrogen (N): 14.0067 amu
      • Sulfur (S): 32.06 amu

    Chemical Formulas

    • Empirical Formula: Represents the simplest whole-number ratio of elements. Example: Hydrogen peroxide (H2O2) has an empirical formula of HO.
    • Molecular Formula: Shows the actual number of atoms of each element in a molecule. Example: Glucose (C6H12O6).
    • Molecular mass calculations:
      • For glucose: C: 6(12.00) + H: 12(1.008) + O: 6(16.00) = 180.096 amu.
      • For naphthalene (C10H8): 120 (C) + 8 (H) = 128 amu.

    Formula Mass vs. Molecular Mass

    • Molecular mass applies to molecular compounds; formula mass applies to ionic compounds.
    • Example of ionic compound: Sodium Chloride (NaCl) has a formula mass of 58.5 amu.
    • Milk of magnesia (Mg(OH)2) formula mass calculated: 24 (Mg) + 32 (O) + 2 (H) = 58 amu.

    Ions and Chemicals

    • Definition of ions: Charged species formed from atoms by adding or removing electrons.
    • Cations: Positively charged (e.g., Na+), Anions: Negatively charged (e.g., Cl-).
    • Ionic compounds consist of equal numbers of cations and anions to maintain neutrality.

    Mole-Particles Calculations

    • Understanding that one mole equals Avogadro's number (6.022 × 10²³):
      • For Zn: 1.25 moles = 7.53 × 10²³ atoms.
      • For Al: 0.2 moles = 1.2044 × 10²³ atoms.
    • Mole calculations for molecules:
      • Methane (CH4): 0.5 moles = 3.011 × 10²³ molecules.
      • Sulfur dioxide (SO2): 0.25 moles = 1.505 × 10²³ molecules.

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    Fundamentals Of Chemistry - Class 9

    Description

    Explore the fascinating story of Archimedes and his renowned method for determining the purity of gold. This quiz delves into the principles of inorganic chemistry, focusing on topics like carbonates, bicarbonates, and the displacement of liquids. Test your knowledge of this significant historical experiment and its scientific implications.

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