Molecules and Molecular Compounds
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Questions and Answers

What type of molecule contains more than two atoms?

  • Covalent molecule
  • Polyatomic molecule (correct)
  • Binary molecular compound
  • Diatomic molecule

    • What determines the order of elements in a molecular compound?

  • The electronegativity of the elements
  • The molecular weight of the compound
  • The group number of the elements (correct)
  • The atomic number of the elements

    • Which of the following is an example of a binary molecular compound?

  • BeO
  • Li2O
  • Cl2
  • N2O3 (correct)

    • What is the name of the process of naming molecular compounds?

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

    Why is the prefix mono- generally omitted for the first element?

    <p>For ease of pronunciation</p> Signup and view all the answers

    What is the purpose of using Greek prefixes in naming binary molecular compounds?

    <p>To specify the number of atoms of each element</p> Signup and view all the answers

    What is the correct order of elements in a molecular compound?

    <p>Element with smallest group number first</p> Signup and view all the answers

    What is special about the naming of oxides?

    <p>The last letter of the prefix is eliminated</p> Signup and view all the answers

    Why is NCl3 named nitrogen trichloride, but AlCl3 is simply aluminum chloride?

    <p>NCl3 is a molecular compound and AlCl3 is an ionic compound</p> Signup and view all the answers

    What type of compound is CoCI2 · 6H2O?

    <p>Hydrated ionic compound</p> Signup and view all the answers

    What is the systematic name for MgSO4 · 7H2O?

    <p>Magnesium sulfate heptahydrate</p> Signup and view all the answers

    What is the meaning of the prefix 'hemi' in hydrate prefixes?

    <p>Half a water molecule</p> Signup and view all the answers

    What is the name of the prefix that represents three water molecules in hydrate prefixes?

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

    What type of compound is CaSO4 · ½H2O?

    <p>Hydrated ionic compound</p> Signup and view all the answers

    What is the systematic name for CaSO4 · ½H2O?

    <p>Calcium sulfate hemihydrate</p> Signup and view all the answers

    What is the general formula for a hydrated ionic compound?

    <p>MX · xH2O</p> Signup and view all the answers

    What is the prefix for the number 9 in binary molecular compounds?

    <p>Nona-</p> Signup and view all the answers

    What is the name of the compound CO2?

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

    What is the correct name of the compound P4S10?

    <p>Tetraphosphorus decasulfide</p> Signup and view all the answers

    What is the correct formula for phosphorus tribromide?

    <p>PBr3</p> Signup and view all the answers

    What is the name of the compound NI3?

    <p>Nitrogen triiodide</p> Signup and view all the answers

    What is the prefix for the number 5 in binary molecular compounds?

    <p>Penta-</p> Signup and view all the answers

    What is the name of the compound SF6?

    <p>Sulfur hexafluoride</p> Signup and view all the answers

    What is the name of the compound PCI5?

    <p>Phosphorus pentachloride</p> Signup and view all the answers

    What is the definition of an acid?

    <p>A substance that produces hydrogen ions when dissolved in water</p> Signup and view all the answers

    What is the rule for naming simple acids?

    <p>Replace the -ide ending with -ic and add the word acid</p> Signup and view all the answers

    What is the name of the acid derived from the oxoanion chlorate?

    <p>Chloric acid</p> Signup and view all the answers

    How is the name of an oxoacid derived when the oxoanion’s name ends in -ite?

    <p>The ending changes to -ous and the word acid is added</p> Signup and view all the answers

    What is the name of the acid derived from the oxoanion perchlorate?

    <p>Perchloric acid</p> Signup and view all the answers

    What is the mass of carbon in 100 g of a compound with 53.31% carbon?

    <p>53.31 g</p> Signup and view all the answers

    What is the name of the acid derived from the oxoanion chlorite?

    <p>Chlorous acid</p> Signup and view all the answers

    What is the general structure of an acid?

    <p>Hydrogen ions attached to an anion</p> Signup and view all the answers

    What is the number of moles of hydrogen in 11.19 g of hydrogen?

    <p>11.10 mol</p> Signup and view all the answers

    What is the rule for deriving the name of an oxoacid when the oxoanion’s name ends in -ate?

    <p>The ending changes to -ic and the word acid is added</p> Signup and view all the answers

    What is the smallest number of moles in the preliminary result of C4.439H11.10O2.219?

    <p>2.219</p> Signup and view all the answers

    What is the empirical formula of a compound with a mass percent composition of 53.31% carbon, 11.19% hydrogen, and 35.51% oxygen?

    <p>C2H5O</p> Signup and view all the answers

    What is the molar mass of oxygen?

    <p>16.00 g/mol</p> Signup and view all the answers

    What is the purpose of dividing each of the numerical results by the smallest number of moles?

    <p>To reduce the subscripts to whole numbers</p> Signup and view all the answers

    What is the number of moles of carbon in 53.31 g of carbon?

    <p>4.439 mol</p> Signup and view all the answers

    What is the result of dividing each of the numerical results by the smallest number of moles?

    <p>C2H5O</p> Signup and view all the answers

    Study Notes

    Molecules and Molecular Compounds

    • A molecule can be of an element (e.g., Cl2, H2) or a compound (e.g., HCl)
    • Diatomic molecules contain two atoms (e.g., HCl, CO, N2)
    • Polyatomic molecules contain more than two atoms (e.g., O3, H2O)

    Molecular Compounds: Formulas and Names

    • The formula for a molecular compound cannot be readily determined from its constituent elements
    • Many different combinations of elements can form unique molecular compounds (e.g., NO, NO2, N2O, N2O3, N2O4, N2O5)
    • Binary molecular compounds are composed of two nonmetals
    • To name the compound, name the element that appears first in the formula, then the second element, changing the ending of its name to -ide

    Naming Binary Molecular Compounds

    • Use Greek prefixes to specify the number of atoms of each element present (e.g., mono- = 1, di- = 2, tri- = 3, tetra- = 4, penta- = 5, hexa- = 6)
    • If there is only one atom of the first element in the formula, the prefix mono- is normally omitted
    • Examples of named compounds:
      • SF6: sulfur hexafluoride
      • CF4: carbon tetrafluoride
      • CO2: carbon dioxide
      • N2O5: dinitrogen pentoxide

    Problem Solving: Naming Molecular Compounds

    • Example 1: NI3 (nitrogen triiodide)
    • Example 2: PCI5 (phosphorus pentachloride)
    • Example 3: P4S10 (tetraphosphorus decasulfide)

    Hydrated Ionic Compounds

    • Hydrates are ionic compounds containing a specific number of water molecules associated with each formula unit
    • Examples:
      • MgSO4 · 7H2O (magnesium sulfate heptahydrate)
      • CoCI2 · 6H2O (cobalt(II) chloride hexahydrate)

    Acids

    • An acid is any substance that produces hydrogen ions (H+) when dissolved in water
    • Acids are molecular compounds, but can be thought of as hydrogen ions attached to an anion
    • Rules for naming simple acids:
      • Remove the -gen ending from hydrogen (leaving hydro-)
      • Change the -ide ending on the anion to –ic
      • Combine the two words, and add the word acid
    • Examples:
      • HF: hydrofluoric acid
      • HCl: hydrochloric acid
      • HBr: hydrobromic acid
      • HI: hydroiodic acid
      • HCN: hydrocyanic acid
      • H2S: hydrosulfuric acid

    Empirical Formula

    • Example: Determine the empirical formula of a compound with a mass percent composition of 53.31% carbon, 11.19% hydrogen, and 35.51% oxygen
    • Calculate the number of moles of each element, then reduce the subscripts to whole numbers to obtain the empirical formula, which in this case is C2H5O

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