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AP Chemistry Unit 2: Molecular and Ionic Compound Structure and Properties

12 questions

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Unit 2: Molecular and Ionic Compound Structure and Properties

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Question 1

The bond angle in $H_{2} O$ ( $\approx 104.5°$ ) is less than the ideal tetrahedral angle of $109.5°$ because:

A.Hydrogen atoms are very small and provide less steric repulsion.B.Lone pairs occupy more space than bonding pairs and compress the H–O–H angle.C.The O–H bonds are polar, causing electrostatic repulsion between the hydrogen atoms.D.Water uses

s p^{2}

hybridization, which gives 120° angles reduced by lone pairs.

Question 2

What is the formal charge on the oxygen atom in $C O_{2}$ (a carbon–oxygen double bond)?

- 2

- 1

0

+ 1

Question 3

Using average bond enthalpies, estimate $Δ H$ for the reaction $H_{2} (g) + C l_{2} (g) \to 2 HCl (g)$ , given: $D (H - H) = 436 kJ/mol$ , $D (Cl - Cl) = 243 kJ/mol$ , $D (H - Cl) = 432 kJ/mol$ .

+ 185 kJ/mol

- 185 kJ/mol

- 679 kJ/mol

+ 247 kJ/mol

Question 4

A student draws a Lewis structure for $N O_{2}^{-}$ (nitrite ion) in which nitrogen forms one single bond to one oxygen and one double bond to the other, with one lone pair on nitrogen. What is the formal charge on the nitrogen in this structure?

+ 1

0

- 1

- 2

Question 5

What is the electron-pair geometry and molecular geometry of $S F_{4}$ ?

A.Tetrahedral; tetrahedralB.Trigonal bipyramidal; trigonal bipyramidalC.Trigonal bipyramidal; see-sawD.Octahedral; square planar

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Question 6

How many lone pairs of electrons are on the central nitrogen atom in $N H_{3}$ ?

0

1

2

3

Question 7

In a Lewis structure, three resonance structures can be drawn for $S O_{3}$ . What is the best interpretation of these structures?

A.The molecule rapidly switches between the three structures.B.The true structure is a hybrid in which the electron density is delocalized equally over all S–O bonds.C.The three structures represent three different

S O_{3}

isomers.D.Only the structure with the fewest formal charges is correct; the others are wrong.

Question 8

Which of the following best explains why ionic compounds have high melting points compared with molecular compounds?

A.Ionic compounds are denser, so more energy is needed to expand the lattice.B.Ionic bonds are covalent in nature and therefore very strong.C.Electrostatic forces between oppositely charged ions in the crystal lattice are very strong.D.Ionic compounds cannot conduct electricity, which raises their melting points.

Question 9

Which hybridization is consistent with a carbon atom that forms two double bonds and no single bonds (as in $C O_{2}$ )?

s p^{3}

s p^{2}

s p

s p^{3} d

Question 10

Which of the following species has a trigonal planar molecular geometry?

N H_{3}

S O_{3}

PC l_{3}

Cl F_{3}

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Question 11

Rank the following in order of increasing bond length: C–C single bond, C=C double bond, $C \equiv C$ triple bond.

C \equiv C < C = C < C - C

C - C < C = C < C \equiv C

C = C < C - C < C \equiv C

D.All are equal because the atoms are the same.

Question 12

Which of the following molecules is polar?

B F_{3}

CC l_{4}

C O_{2}

H_{2} S

AP Chemistry Unit 2: Molecular and Ionic Compound Structure and Properties — Free with Answer Explanations | Test Practice Hub