Chemistry Chapter 3 and 4 Exam Review
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Questions and Answers

Which of the statements concerning chemical bonds is false?

  • The sharing of electrons between two nonmetal atoms results in a covalent bond.
  • The attraction between oppositely charged ions results in an ionic bond.
  • A bond dipole is the separation of charge that results when atoms sharing electrons have different electronegativities.
  • The term nonpolar is used to describe a covalent bond in which electrons are not shared equally. (correct)

    • What is the Lewis structure for chloroethylene (C2H3Cl)?

    H H H-C=C-Cl

    What is the molecular shape around the phosphorus atom in PH3?

  • Bent
  • Trigonal planar
  • Trigonal pyramidal
  • Tetrahedral (correct)
  • Linear (correct)

    • Which of the following molecule(s) is(are) polar?

    <p>CHBr3</p> Signup and view all the answers

    Which is the correct Lewis structure for OBr-?

    <p>[O(4 dots)=Br(4 dots)]-</p> Signup and view all the answers

    Which bond is the MOST polar?

    <p>C-F</p> Signup and view all the answers

    What is the molecular shape around the nitrogen atom in the structure shown below? S-H H-C-O-H H-N=C-H

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

    What is the molecular shape around the oxygen atom in the structure shown below? S-H H-C-O-H H-N=C-H

    <p>Trigonal pyramidal</p> Signup and view all the answers

    Which molecule's Lewis structure contains an atom that violates the octet rule?

    <p>BeH2</p> Signup and view all the answers

    Which compound has the greatest number of valence electrons?

    <p>All of the molecules have the same number of valence electrons.</p> Signup and view all the answers

    Which Lewis structure is incorrect?

    <p>Cl-N=N-Cl Cl Cl</p> Signup and view all the answers

    The Lewis structure shown below is not a valid Lewis structure. What statement best describes the error in the structure? Cl-N=N-Cl Cl Cl

    <p>The nitrogen atoms violate the octet rule.</p> Signup and view all the answers

    Considering the electronegativity values indicated for each element, which covalent bond has the LEAST degree of polarity?

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

    The Lewis structure of formaldehyde is shown below. Which statement concerning this structure is INCORRECT? O H-C-H

    <p>The oxygen and carbon atoms each have an octet of electrons in their valence shells.</p> Signup and view all the answers

    Which statement concerning the ion Li+ is correct?

    <p>Li+ has two total electrons.</p> Signup and view all the answers

    What is the electron configuration of an F- ion?

    <p>1s(to the 2nd)2s(to the 2nd)2p(to the 6th)</p> Signup and view all the answers

    What is the ion symbol for an atom with twenty (20) protons and eighteen (18) electrons?

    <p>Ca2+</p> Signup and view all the answers

    What is the ion symbol for an atom with sixteen (16) protons and eighteen (18) electrons?

    <p>S2-</p> Signup and view all the answers

    How many protons and electrons are present in Co2+?

    <p>27 protons, 25 electrons</p> Signup and view all the answers

    What is the formula for the ionic compound lithium oxide?

    <p>Li2O</p> Signup and view all the answers

    Which statement best explains the basis for the octet rule?

    <p>Atoms are most stable with eight electrons in their valence shell and the electron configuration of a noble gas.</p> Signup and view all the answers

    What is the formula for the ionic compound formed when aluminum and sulfur combine?

    <p>Al2S3</p> Signup and view all the answers

    What is the chemical formula of tin (IV) cyanide?

    <p>Sn(CN)4</p> Signup and view all the answers

    The formula for zinc acetate is ________.

    <p>Zn(CH3CO2)2</p> Signup and view all the answers

    Which chemical formula is NOT correct?

    <p>More than one of the formulas is not correct.</p> Signup and view all the answers

    Which chemical formula is correct?

    <p>Mg(OH)2</p> Signup and view all the answers

    What is the name of the compound (NH4)2SO4?

    <p>Ammonium sulfate</p> Signup and view all the answers

    Which compound has the highest melting point?

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

    What is the charge on the chromium ion in the ionic compound CrCl3?

    <p>+3</p> Signup and view all the answers

    What is the formula for the ionic compound formed from the lead (II) ion and the carbonate ion?

    <p>PbCO3</p> Signup and view all the answers

    What is the formula for chromous cyanide?

    <p>Cr(CN)2</p> Signup and view all the answers

    The diphosphate ion is a biologically important polyatomic ion. If the ionic compound calcium diphosphate has the formula Ca2P2O7, which correctly represents the ion symbol of the diphosphate ion?

    <p>P2O7(to the 2-)</p> Signup and view all the answers

    The correct name for AuI3 is ________.

    <p>Gold (III) iodide</p> Signup and view all the answers

    The correct name for Ag2O is ________.

    <p>Silver (I) oxide</p> Signup and view all the answers

    Study Notes

    Chemical Bonds

    • Atoms with five valence electrons generally form three covalent bonds.
    • The sharing of electrons between nonmetals results in covalent bonds while the attraction between oppositely charged ions results in ionic bonds.
    • Nonpolar covalent bonds are characterized by equal sharing of electrons, and a bond dipole occurs when atoms have differing electronegativities.

    Molecular Structures and Geometry

    • Formaldehyde (CH2O) has 12 valence electrons.
    • Chloroethylene (C2H3Cl) can be represented with the Lewis structure H-C=C-Cl.
    • Carbonic acid has bond angles around the carbon atom of 120° due to its trigonal planar geometry.
    • Aspartic acid requires 4 lone pairs of electrons to complete its structure.

    Molecular Shapes

    • The molecular shape around a phosphorus atom in PH3 is trigonal pyramidal.
    • The nitrogen atom in NH3 exhibits a trigonal pyramidal shape.
    • The bond angles around sulfur in certain organic compounds measure approximately 109.5°.

    Polarity in Molecules

    • Molecules CBr3 and others may be polar based on their structure and electronegativity values.
    • The most polar bond among given options is C-F, due to the significant difference in electronegativity.

    Lewis Structures

    • Valid Lewis structures respect the octet rule, while incorrect structures may violate this principle.
    • The Lewis structure of OBr- includes a charge indicating additional electrons.

    Valence Electrons and Electron Configuration

    • Lithium ions (Li+) have 2 total electrons, and fluorine ions (F-) have a configuration of 1s² 2s² 2p⁶.
    • An atom with 20 protons and 18 electrons is denoted as Ca²⁺, while an atom with 16 protons and 18 electrons is represented as S²⁻.

    Ionic Compounds

    • The ionic compound lithium oxide is represented by the formula Li2O.
    • When aluminum and sulfur combine, the formula is Al2S3.
    • Sn(CN)4 represents tin (IV) cyanide.

    Chemical Naming and Formula Accuracy

    • (NH4)2SO4 is named ammonium sulfate.
    • AuI3 is classified as gold (III) iodide, while Ag2O is known as silver (I) oxide.
    • The charge on the chromium ion in CrCl3 is +3.

    Melting Points and Ionic Compounds

    • KCl has a higher melting point compared to other organic or molecular substances listed, due to strong ionic bonds.
    • The formula for the ionic compound containing lead (II) and carbonate ions is PbCO3.

    Polyatomic Ions

    • Calcium diphosphate is represented as Ca2P2O7, indicating the diphosphate ion as P2O7²⁻.

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    Prepare for your upcoming Chemistry exam with this interactive flashcard review covering Chapters 3 and 4. Test your understanding of covalent bonds and the characteristics of chemical bonding with multiple-choice questions.

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