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?

CHBr3 Signup and view all the answers

Which is the correct Lewis structure for OBr-?

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

Which bond is the MOST polar?

C-F 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

Linear 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

Trigonal pyramidal Signup and view all the answers

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

BeH2 Signup and view all the answers

Which compound has the greatest number of valence electrons?

All of the molecules have the same number of valence electrons. Signup and view all the answers

Which Lewis structure is incorrect?

Cl-N=N-Cl Cl Cl 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

The nitrogen atoms violate the octet rule. Signup and view all the answers

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

F-F 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

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

Which statement concerning the ion Li+ is correct?

Li+ has two total electrons. Signup and view all the answers

What is the electron configuration of an F- ion?

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

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

Ca2+ Signup and view all the answers

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

S2- Signup and view all the answers

How many protons and electrons are present in Co2+?

27 protons, 25 electrons Signup and view all the answers

What is the formula for the ionic compound lithium oxide?

Li2O Signup and view all the answers

Which statement best explains the basis for the octet rule?

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

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

Al2S3 Signup and view all the answers

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

Sn(CN)4 Signup and view all the answers

The formula for zinc acetate is ________.

Zn(CH3CO2)2 Signup and view all the answers

Which chemical formula is NOT correct?

More than one of the formulas is not correct. Signup and view all the answers

Which chemical formula is correct?

Mg(OH)2 Signup and view all the answers

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

Ammonium sulfate Signup and view all the answers

Which compound has the highest melting point?

KCl Signup and view all the answers

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

+3 Signup and view all the answers

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

PbCO3 Signup and view all the answers

What is the formula for chromous cyanide?

Cr(CN)2 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?

P2O7(to the 2-) Signup and view all the answers

The correct name for AuI3 is ________.

Gold (III) iodide Signup and view all the answers

The correct name for Ag2O is ________.

Silver (I) oxide 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.