Temperature Conversions and Scientific Notation
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Questions and Answers

What is the conversion of 25°C into Kelvin?

  • 273K
  • 298K (correct)
  • 310K
  • 250K

    • Which of the following represents the conversion of 100K into Celsius?

  • -173°C (correct)
  • -100°C
  • 100°C
  • 173°C

    • What is the correct Fahrenheit equivalent of 100°C?

  • 212°F (correct)
  • 37°F
  • 100°F
  • 320°F

    • Which of the following is the scientific notation for 0.00025?

    <p>2.5 x 10^-4</p> Signup and view all the answers

    What is the significant figure count for the number 100.0?

    <p>4</p> Signup and view all the answers

    How many significant figures are in the number 0.003?

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

    Which statement correctly defines precision?

    <p>Closeness of multiple measurements to each other</p> Signup and view all the answers

    What is the scientific notation for the number 3625?

    <p>3.625 x 10^3</p> Signup and view all the answers

    What is the result of rounding 5.675 to 3 significant figures?

    <p>5.67</p> Signup and view all the answers

    Which of the following statements best represents the law of conservation of mass?

    <p>Matter cannot be created or destroyed during a chemical reaction.</p> Signup and view all the answers

    How many grams of oxygen combine with 2 grams of hydrogen to form water?

    <p>16 grams</p> Signup and view all the answers

    What does Gay Lussac's law state about gases in a reaction?

    <p>They combine in a simple ratio if at the same temperature and pressure.</p> Signup and view all the answers

    What is Avogadro's Law primarily concerned with?

    <p>The volume and number of gas molecules.</p> Signup and view all the answers

    What is the correct rounding of 4.28 to 2 significant figures?

    <p>4.3</p> Signup and view all the answers

    Which statement correctly describes Dalton's atomic theory?

    <p>All atoms of a given element are identical in mass.</p> Signup and view all the answers

    What does atomic mass measure?

    <p>Ratio of average mass of an atom to carbon-12 isotope.</p> Signup and view all the answers

    What is the molar mass of ammonia (NH3)?

    <p>17 g</p> Signup and view all the answers

    What is the mass percentage of hydrogen in ethanol (C2H5OH)?

    <p>13.04%</p> Signup and view all the answers

    Which of the following represents the empirical formula of a compound with 4.07% hydrogen, 24.27% carbon, and 71.65% chlorine?

    <p>CH<sub>2</sub>Cl</p> Signup and view all the answers

    What is the mass percentage of oxygen in sodium hydroxide (NaOH)?

    <p>40%</p> Signup and view all the answers

    If a compound has a molar mass of 98.96 g and an empirical formula mass of 49.48 g, what is the value of 'n' used to determine the molecular formula?

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

    What is the mass percentage of nitrogen in ammonia (NH3)?

    <p>82.35%</p> Signup and view all the answers

    How many moles of carbon are present in the compound with a molar mass of 98.96 g and 24.27% carbon?

    <p>2.02</p> Signup and view all the answers

    Which atom ratios help define the empirical formula?

    <p>Simplest whole number ratio</p> Signup and view all the answers

    What is the molecular mass of water (H2O)?

    <p>18u</p> Signup and view all the answers

    Which element has an atomic mass of approximately 24?

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

    What is the molar mass of sulfuric acid (H2SO4)?

    <p>98g</p> Signup and view all the answers

    What percentage of mass does hydrogen contribute to water (H2O)?

    <p>11.11%</p> Signup and view all the answers

    What is the molecular mass of carbon dioxide (CO2)?

    <p>44u</p> Signup and view all the answers

    Which compound has a molar mass of 106g?

    <p>Sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>)</p> Signup and view all the answers

    What is the atomic mass of iron (Fe)?

    <p>56</p> Signup and view all the answers

    What is the mass percentage of oxygen in sulfur dioxide (SO2) if its molar mass is 64g?

    <p>62.5%</p> Signup and view all the answers

    What is the empirical formula of the compound described?

    <p>CH<sub>2</sub>O</p> Signup and view all the answers

    How do you calculate the molar mass of water (H2O)?

    <p>(2 x 1) + (16) = 18 g</p> Signup and view all the answers

    What is the molecular formula of the compound derived from the empirical formula CH2O and a molar mass of 90 g?

    <p>C<sub>3</sub>H<sub>6</sub>O<sub>3</sub></p> Signup and view all the answers

    How many molecules are present in 10 grams of water?

    <p>3.345 x 10<sup>23</sup></p> Signup and view all the answers

    What is the total number of moles in 20 grams of NaOH?

    <p>1 mole</p> Signup and view all the answers

    During the combustion of methane (CH4), what are the products formed?

    <p>Carbon dioxide and water</p> Signup and view all the answers

    Which reaction demonstrates the decomposition of calcium carbonate?

    <p>CaCO<sub>3</sub> → CaO + CO<sub>2</sub></p> Signup and view all the answers

    Calculate the molar mass of sodium carbonate (Na2CO3).

    <p>106 g</p> Signup and view all the answers

    Study Notes

    Temperature Conversions

    • Converting Celsius (°C) to Kelvin (K): Add 273 to the Celsius temperature.
      • 25°C = 298K
      • 37°C = 310K
      • 110°C = 373K
      • 0°C = 273K
    • Converting Kelvin (K) to Celsius (°C): Subtract 273 from the Kelvin temperature.
      • 100K = -173°C
      • 373K = 100°C
      • 400K = -127°C
    • Converting Celsius (°C) to Fahrenheit (°F): Multiply the Celsius temperature by 9/5 and then add 32.
      • 25°C = 77°F
      • 100°C = 212 °F

    Scientific Notation

    • Scientific notation expresses numbers as a product of a number between 1 and 10 and a power of 10.
    • 0.003 = 3 x 10-3
    • 0.00025 = 2.5 x 10-4
    • 0.00000089 = 8.9 x 10-7
    • 0.101 = 1.01 x 10-1
    • 1000 = 1 x 103
    • 265 = 2.65 x 102
    • 3625 = 3.625 x 103
    • 465 = 4.65 x 102
    • 25 = 2.5 x 101

    Precision and Accuracy

    • Precision refers to how close multiple measurements of the same quantity are to each other.
    • Accuracy refers to how close a measurement is to the true value.
    • Example:
      • 83.4% represents the precision value.
      • 83% represents the accuracy value.

    Significant Figures

    • Significant figures are the meaningful digits in a number that are known with certainty.

    • Rules for Significant Figures

      • All non-zero numbers are significant. (Example: 283 has 3 significant figures)
      • Zeroes before a number are not significant. (Examples: 0.003 has 1 significant figure, 0.012 has 2 significant figures)
      • Zeroes between non-zero numbers are significant. (Examples: 101 has 3 significant figures, 320059 has 6 significant figures)
      • Zeroes to the right of a number are non-significant unless there's a decimal point. (Examples: 100 has 1 significant figure, 100.0 has 4 significant figures)

    • Significant figures in the following numbers:

      • 0.002 = 1 significant figure
      • 0.32 = 2 significant figures
      • 10101 = 5 significant figures
      • 239 = 3 significant figures
      • 100 = 1 significant figure
      • 100.0 = 4 significant figures
      • 2.60201 = 6 significant figures
      • 2.01 x 105 = 3 significant figures

    • Rounding numbers to 3 significant figures:

      • 2.463 = 2.46
      • 3.167 = 3.17
      • 284.3 = 284
      • 4.645 = 4.64
      • 5.675 = 5.67

    • Rounding numbers to 2 significant figures:

      • 3.62 = 3.6
      • 4.28 = 4.3
      • 7.89 = 7.9
      • 5.25 = 5.2
      • 5.35 = 5.3

    Law of Chemical Combination

    • Law of Conservation of Mass: Matter cannot be created or destroyed in chemical reactions. (Proposed by Antoine Lavoisier in 1789)
    • Law of Definite Proportion: A given compound always has the same proportion of elements by weight.
    • Law of Multiple Proportion: When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other element are in a simple ratio of whole numbers.
      • Example: Water (H2O) and Hydrogen Peroxide (H2O2)
    • Gay-Lussac's Law of Combining Volumes: When gases react, their volumes combine in a simple ratio provided they are at the same temperature and pressure.
      • Example: H2 + O2 → 2H2O (2 volumes of hydrogen + 1 volume of oxygen → 2 volumes of water)
    • Avogadro's Law: Equal volumes of gases at the same temperature and pressure contain the same number of molecules.

    Dalton's Atomic Theory

    • Matter is composed of indivisible particles called atoms.
    • Atoms of the same element have identical properties and masses.
    • Atoms of different elements have different properties and masses.
    • Compounds are formed when atoms of different elements combine in fixed ratios.
    • Chemical reactions involve the rearrangement of atoms; they are neither created nor destroyed.

    Atomic Mass

    • Atomic mass: The average mass of an atom of an element relative to 1/12 the mass of a carbon-12 atom.
    • Unit: 1 amu or 'U'
    • Examples:
      • Hydrogen (H): 1 amu
      • Carbon (C): 12 amu
      • Oxygen (O): 16 amu

    Molecular Mass

    • Molecular mass: The sum of the atomic masses of all the atoms in a molecule.
    • Examples:
      • H2: 2 x 1 = 2 u
      • CH4: 12 + (4 x 1) = 16 u
      • H2O: (2 x 1) + 16 = 18 u
      • NaCl: 23 + 35.5 = 58.5 u
      • H2SO4: (2 x 1) + 32 + (4 x 16) = 98 u
      • C6H12O6: (6 x 12) + (12 x 1) + (6 x 16) = 180 u
      • CO2: 12 + (2 x 16) = 44 u
      • NH3: 14 + (3 x 1) = 17 u
      • Na2CO3: (23 x 2) + 12 + (3 x 16) = 106 u
      • NaHCO3: 23 + 1 + 12 + (3 x 16) = 84 u
      • C2H2OH: (2 x 12) + (2 x 1) + 16 + 1 = 46 u
      • CH3OH: 12 + (3 x 1) + 16 + 1 = 32 u

    Mole Concept

    • Mole (mol): The amount of substance that contains as many elementary entities (atoms, molecules, ions, etc.) as there are atoms in 0.012 kilogram of carbon-12.
    • Avogadro Constant (NA): 6.022 x 1023 entities per mole.
    • Molar Mass: The mass of one mole of a substance in grams.
    • Examples:
      • Molar mass of H2SO4: 98 g
      • Molar mass of Na2CO3: 106 g
      • Molar mass of H2O: 18 g

    Percentage Composition

    • Formula: Mass % of an element = (Mass of the element / Molar mass of the compound) x 100
    • Examples:
      • Water (H2O):
        • Mass % of hydrogen: (2 x 1 / 18) x 100 = 11.11%
        • Mass % of oxygen: (16 / 18) x 100 = 88.88%
      • Ammonia (NH3):
        • Mass % of nitrogen: (14 x 100 / 17) = 82.35%
        • Mass % of hydrogen: (3 x 1 x 100 / 17) = 17.64%
      • Ethanol (C2H5OH):
        • Mass % of carbon: (2 x 12 x 100 / 46) = 52.17%
        • Mass % of hydrogen: (6 x 1 x 100 / 46) = 13.04%
        • Mass % of oxygen: (16 x 100 / 46) = 34.78%
      • Sodium Hydroxide (NaOH):
        • Mass % of sodium: (23 x 100 / 40) = 57.5%
        • Mass % of oxygen: (16 x 100 / 40) = 40%
        • Mass % of hydrogen: (1 x 100 / 40) = 2.5%
      • Methanol (CH3OH):
        • Mass % of hydrogen: (4 x 1 x 100 / 32) = 12.5%
        • Mass % of carbon: (12 x 100 / 32) = 37.5%
        • Mass % of oxygen: (16 x 100 / 32) = 50%

    Empirical Formula and Molecular Formula

    • Empirical formula: The simplest whole number ratio of different atoms in a compound.

    • Molecular formula: The actual number of different atoms present in a molecule of a compound.

    • Example: A compound with 4.07% hydrogen, 24.27% carbon, and 71.65% chlorine has a molar mass of 98.96 g.

      • Empirical Formula: CH2Cl
      • Molecular Formula: C2H4Cl2

    • Example: An organic compound with 39.9% carbon, 6.7% hydrogen, and 53.4% oxygen has a molar mass of 90 g.

      • Empirical Formula: CH2O
      • Molecular Formula: C3H6O3

    Molar Volume

    • Molar volume: The volume occupied by one mole of any substance.
    • Volume of 1 mole of gas at STP: 22.4 liters (Standard Temperature and Pressure: 0°C and 1 atm)
    • Example: Calculate the number of molecules in 10g of water.
      • 18 g of H2O contains 6.022 x 1023 molecules.
      • 10 g of H2O contains: (10 x 6.022 x 1023 / 18) = 3.345 x 1023 molecules.
    • Example: Calculate the number of moles in 20 g of NaOH.
      • 40 g of NaOH contains 6.022 x 1023 molecules.
      • 20 g of NaOH contains: (20 x 6.022 x 1023 / 40) = 3.011 x 1023 molecules.
    • Example: Calculate the number of moles in 40 g of CH3OH.
      • 32 g of CH3OH contains 6.022 x 1023 molecules.
      • 40 g of CH3OH contains: (40 x 6.022 x 1023 / 32) = 7.338 x 1023 molecules.
    • Example: Calculate the number of moles in 18g of Na2CO3
      • 106 g of Na2CO3 contains 6.022 x 1023 molecules.
      • 18 g of Na2CO3 contains: (18 x 6.022 x 1023 / 106) = 1.022 x 1023 molecules.

    Stoichiometric Calculations

    • Stoichiometry: The branch of chemistry dealing with quantitative relationships between reactants and products in chemical reactions.

    • Balanced Chemical Equations: Equations that show the exact number of atoms and molecules involved in a chemical reaction.

    • Examples of Balanced Chemical Equations:

      • Combustion of methane: CH4 + 2O2 → CO2 + 2H2O
      • Decomposition of calcium carbonate: CaCO3 → CaO + CO2
      • Combustion of magnesium oxide: 2Mg + O2 → 2MgO

    • Example: Calculate the amount of water produced by the combustion of 18 g of methane.

      • CH4 + 2O2 → CO2 + 2H2O
      • 1 mole of CH4 (16 g) produces 2 moles of H2O (36 g)
      • 18 g of CH4 produces: (18 g x 36 g / 16 g) = 40.5 g of water.

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    Description

    This quiz covers the essential methods for converting temperatures between Celsius, Kelvin, and Fahrenheit, along with the fundamentals of scientific notation. Test your understanding of how to accurately convert and represent numbers in various formats, as well as the concepts of precision and accuracy in measurements. Perfect for students looking to solidify their grasp on these critical topics.

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