2.9 MC Answers and Review

⛔STOP ! ⛔ Before you look at the answers, make sure you gave this practice quiz a try so you can assess your understanding of the concepts covered in Unit 2. Click here for the practice questions: AP Chemistry Unit 2 Multiple Choice Questions.

Facts about the test: The AP Chemistry exam has 60 multiple choice questions and you will be given 1 hour 30 minutes to complete the section. That means it should take you around 15 minutes to complete 10 questions.

B. Both molecules have the same shape because the molecular formulas are the same.

C. Both molecules have similar shapes and are nonpolar because the electronegativities for C and S are similar.

D. The lone pairs on S make is the negative end of the dipole.

Answer: An electron domain is a lone pair or a bonding group. The two molecules have different shapes because the total number of electron domains are different.

📄 Study AP Chem, Unit 2.5: Lewis Dot Diagrams

A. NaCl

B. KF

C. K_2O

Answer: The lattice energy for CaO is greatest because the magnitude of charge difference is greatest between the Ca^2+ ions and the O^2- ions. As lattice energy increases, the melting point of the ionic compound increases.

📄 Study AP Chem, Unit 2.3: Ionic Bonding and Ionic Solids

A. 2 sigma and 1 pi bond

C. 3 sigma bonds only

D.3 pi bonds only

Answer: In the Lewis structure, there are 2 single bonds and 1 double bond. For every single bond there is 1 sigma bond. For every double bond, there is 1 sigma bond and 1 pi bond.

📄 Study AP Chem, Unit 2.7: VSEPR, Bond Hybridization, and Molecular Geometry

A. Gold, Au(s)

B. Ammonium Nitrate, NH_4NO_3(s)

D. Potassium Chloride, KCl(s)

Answer: Covalent compounds have relatively low melting and boiling points compared to ionic compounds and metallic solids. The only covalent compound is ethanol.

📄 Study AP Chem, Unit 2.4: Metallic Bonding and Alloys

A. Bond Length

B. Electronegativity

D. Type of Bond

Answer: The potential energy on the y-axis measures the bond energy, the amount of energy required to separate the two oxygen atoms.

📄 Study AP Chem, Unit 2.2: Intramolecular Force and Potential Energy

A. The P--F bonds are nonpolar while the P--Cl bonds are polar

C. P--F is a single bond while P--Cl is a double bond.

D. P--Cl is an ionic bond while P--F is a covalent bond.

Answer: Symmetrical molecules are nonpolar regardless of the type of bonds. Unsymmetrical molecules, like PCl_3, are polar if the bonds have a significant electronegativity difference.

📄 Study AP Chem, Unit 2.7: VSEPR, Bond Hybridization, and Molecular Geometry

A. CBr_4 is an electrolyte.

B. CBr_ 4 is a solid at room temperature and is hard, but brittle.

C. CBr_4 is malleable, ductile, and lustrous.

Answer: CBr_4 is a covalent molecule; therefore, it has a relatively low boiling point and cannot conduct electricity. 

📄 Study AP Chem, Unit 2.1: Types of Chemical Bonds

A.  Trigonal Pyramidal

C. Tetrahedral

D. Linear

Answer: Formaldehyde's Lewis structure contains three bonding groups and no lone pairs. This is consistent with trigonal planar molecular geometry.

📄 Study AP Chem, Unit 2.7: VSEPR, Bond Hybridization, and Molecular Geometry

B. Mo is a gas at room temperature.

C. Mo is a solid at room temperature and is hard, but brittle.

D. Mo has a boiling point of 97C and cannot conduct electricity.

Answer: Molybdenum is a metal. Metals are located on the left side of the periodic table and tend to be malleable, ductile, and lustrous.

📄 Study AP Chem, Unit 2.4: Metallic Bonding and Alloys

A. NH_3

B.CCI_4

C.SF_2

Answer: SO_2 is the only molecule in the list that has a resonance structure. Remember resonance structures are when there is more than one appropriate Lewis structure.

📄 Study AP Chem, Unit 2.6: Resonance and Formal Charge

A. sp 

C. sp^3

D. SO_3 does not have hybridization because it has a resonance structure.

Answer: The hybridization for SO_3 is sp^2 because the molecule has three electron domains. The completed Lewis structure contains three bonds to oxygen and no lone pairs.  

📄 Study AP Chem, Unit 2.7: VSEPR, Bond Hybridization, and Molecular Geometry

B. Brass (Cu & Zn)

C. Sodium chloride (NaCl)

D. Dry Ice (CO_2)

Answer: Steel is an interstitial alloy. Interstitial alloys are more rigid than pure metals and substitutional alloys because the smaller atoms fit in the holes created by the parent atoms. This makes it difficult for the host atom to move around. 

📄 Study AP Chem, Unit 2.4: Metallic Bonding and Alloys

A. Al_3Cl

B. AlCl

C. AlCl_2

Answer: When aluminum is in an ionic compound, it has a charge of 3+. When chlorine is in an ionic compound, it has a charge of 1-. Therefore the ratio that elements come in to make a neutral compound is 1 Al: to 3 Cl ions.  

📄 Study AP Chem, Unit 2.3: Ionic Bonding and Ionic Solids

A. Diamond (C)

B. Ethanol (CH_3OH)

D. Potassium bromide (KBr)

Answer: Zinc is a metal. Metals are the only substance that conduct electricity in the solid phase.

📄 Study AP Chem, Unit 2.7: VSEPR, Bond Hybridization, and Molecular Geometry

B. Ionic Solid

C. Molecular Solid

D. Metallic Solid

Answer: Network covalent solids are giant molecules. In order to melt them, the bonds between the atoms must be broken, which requires more energy than overcoming intermolecular forces.

📄 Study AP Chem, Unit 2.4: Metallic Bonding and Alloys

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