Chemistry Midterm 3

Rank the following in chronological order of their discovery (from oldest to newest): I. Livermorium (element 116) II. Copper III. Electron

(oldest) II < III < I (newest)

According to molecular orbital theory, rank C22+, C2, and C22 − by increasing bond length. (question 29 M3V1)

(shortest) C22- < C2 < C22+ (longest)

When the nitrogen-oxygen bonds in NO+, NO2−, and NO3− are arranged in order of increasing bond length, what is the correct order?

(shortest) NO+ < NO2− < NO3−(longest)

Arrange the following atoms in order of increasing size: C, F, and Si.

(smallest) F < C < Si (largest)

The dipole moment of ClF(g) is 0.88 D and the bond length is 1.63 Å. Calculate the partial charge on the Cl atom.(1 D = 3.34 × 10−30 C•m; 1 e− = 1.60 × 10−19 C)

+0.11

Use bond enthalpy data to approximate the enthalpy change for the COMBUSTION of 1 mole of C2H4 (g) in excess oxygen. Average Bond Enthalpy values (kJ/mol) C-H: 413 kJ/mol C-O: 358 kJ/mol C=O: 799 kJ/mol C-C: 348 kJ/mol C=C: 614 kJ/mol O-H: 463 kJ/mol O=O: 495 kJ/mol

-1297kj/mol

Use the provided bond enthalpies to estimate the ∆H of the reaction below: CH3Cl(g) + F2(g) → CH2FCl(g) + HF(g) Bond enthalpy values: C-H = 414 kJ/mol, H-F = 565 kJ/mol, C-Cl = 331 kJ/mol, C-F = 439 kJ/mol, F-F = 158 kJ/mol

-432

What is the standard enthalpy of formation for CaCl2(s)? (Question 8 M3V3)

-795

How many electrons are in the π system of NO3−?

6

How many lone pairs of electrons are found in BrCl?

6

Given the following information, calculate the lattice energy for KBr(s). Potassium Bromine ∆H°f [K(g)] = 90 kJ/mol ∆H°f [Br2(g)] = 111.8 kJ/mol 1st ionization energy = 419 kJ/mol 1st ionization energy = 1140 kJ/mol 1st electron affinity = −48 kJ/mol 1st electron affinity = −325 kJ/mol Other KBr(s): ∆H° f = −392 kJ/mol Br-Br(g): bond dissociation energy = 193 kJ/mol

728kj/mol

Which of the following compounds has the largest lattice energy? a. LiBr b. CsBr c. CaCl2 d. CaO

CaO

Which of these elements has the lowest melting point? a. Na b. I c. Cl d. Rb

Cl

In its most common oxidation state, which of these metals does not achieve a noble gas configuration? Co Al K Ca

Co

According to VSEPR theory, given the two molecules below, which bond angle is the smallest? (look at question 22 M3 V1) a. H-B-H b. H-C-H c. H-C-O d. all the bonds are equal

H-C-H

When the carbon-oxygen bonds in H3COH, H2CO, and CO32− are arranged in order of increasing bond length, what is the correct order?

H2CO < CO32− < H3COH

What is the dominant Lewis structure for N2O? (question 35 M3V3)

IV

Based on their positions in the periodic table, arrange the following ions in order of increasing radii. Se2-, S2-, Cl-, K+

K+ < Cl− < S2− < Se2−

Which of the following has the smallest lattice energy? ScN MgO BaCl2 LiF

LiF

Draw a pi* bond

Look at notes

Which species requires resonance to explain the fact that all bond lengths within the species are equal in length? NF3 NH4+ NO2+ NO2−

NO2-

Which molecule(s) is(are) known to exist? I. SF4 II. OF4

Only I

Which molecule(s) is(are) planar? I. Diazene (N2H2) II. Ethane (C2H6)

Only I

Given the figure below, which of the following is a periodic trend? I. Zeff for 1s electrons. II. Zeff for valence electrons. (question 31 M3V3)

Only II

Identify the metal with the highest reactivity, which is attributed to the ease with which it loses electrons. Li Rb Ca Sr

Rb

Which species has the same molecular/ionic geometry as the NO3− ion? SO3 SO32− ClF3 ClO3−

SO3

Which of the following is the best Lewis structure for hydroxylamine, which has a formula of OH3N? (Question 15 M3 V1) look up

Structure 3

Which reaction corresponds to the second electron affinity of S?

S−(g) + e− → S2−(g)

What is the shape of the ClF3 molecule?

T-shaped

The figure shows the overlap of two hybrid orbitals to form a bond in a hydrocarbon. What type of bond is shown? (question 31 M3V2) a. C-C σ bond b. C-C π bond c. C-H σ bond d. Both a C-C σ and a C-C π bond are shown.

a

The structures of molecular oxygen (O2) and ozone (O3) are provided below. (question 23 M3V2) The bond length of the oxygen-oxygen bond in O2 is ______ than the oxygen-oxygen bond in ozone. The strength of the oxygen-oxygen bond in O2 is ______ than the oxygen-oxygen bond in ozone. a. shorter; stronger b. shorter; weaker c. longer; stronger d. longer; weaker

a

What is the relationship between the value for the first ionization energy of Br−(g) ion and the electron affinity of Br(g)? a. The magnitudes are the same, but they have opposite signs. b. The magnitude of the first ionization energy is greater than the magnitude of the electron affinity. c. The magnitude of the electron affinity is greater than the magnitude of the first ionization energy. d. The magnitudes are the same and they have the same signs.

a

Which of the following shows the correct relationship between the first ionization energies of the given elements? a. Ne > F b. Li > Be c. Ga > Ge d. Xe > Ne

a

With respect to the carbon-oxygen bonds, CO32- has a __________ bond length and a __________ bond order compared to H2CO. a. longer; larger b. longer; smaller c. smaller; larger d. smaller; smaller

b

Which of these periodic trends has the strongest influence on the first ionization energy of an atom? a. electronegativity b. electron affinity c. atomic radius d. atomic weight

c

Which of these reactions results in the solution becoming more acidic? a. CaO(s) + H2O(l) → b. NaO(s) + HNO3(aq) → c. P4O10(s) + H2O(l) → d. CO2(g) + NaOH(aq) →

c

Which reaction corresponds to the third ionization energy for Al? a. Al(g) → Al3+(g) + 3 e− b. Al3+(s) + 3 e− → Al(s) c. Al2+(g) → Al3+(g) + e− d. Al2+(s) → Al3+(s) + e−

c

Which type of bonds best describes the bonding in NF3? a. sp3−1s b. sp2−1s c. sp3−2p d. sp2−2p

c

Of these elements, which has the most polar covalent bond when bonded to hydrogen? a. cl b. p c. c d. h

cl

Compared to the alkali metals, which property of hydrogen best accounts for the fact that hydrogen is not a metal? a. ionization energy b. electron configuration c. atomic radius d. effective nuclear charge

ionization energy

Among K, Ca, K+, and Ca2+ label the smallest and largest

largest: k smallest: ca2+

The Born-Haber cycle applies Hess's law to calculate which property than cannot be determined directly experimentally? a. lattice energy b. ionization energy c. standard enthalpy of formation d. bond enthalpy

lattice energy

Construct the Born-Haber cycle for NaCl(s) from the elements and determine which combination of atoms and/or ions have the highest energy. (question 11 M3V2)

look at quiz please

Which of these elements is typically found with oxidation numbers of +5 or +3? a. Sb b. Al c. In d. Zn

sb

What is the molecular geometry of TeF4

see-saw

Identity of the molecular orbital shown below. (question 27 M3V3)

sigma *

The electron domain geometry of IF4+ is __________.

trigonal bipyramidal

Which of the following steps in the Born-Haber cycle represents the ∆H associated with electron affinity? ∆H1 ∆H2 ∆H3 ∆H4

∆H4

How many DELOCALIZED pi electrons are present in CH3COOH? How many in CH3COO-?

CH3COOH: Zero, CH3COO−: Two

Consider the following molecular orbital diagram for O2. Which molecular orbital below corresponds to the molecular orbital labeled with the number 3? (question 30 M3V3)

III

Which of the following molecules is(are) nonpolar as drawn? (question 9 M3V3)

III

What is the ground-state electron configuration of Sn2+? a. [Kr] 4d105p2 b. [Kr] 5s24d85p2 c. [Kr] 5s24d10 d. [Kr] 5s14d105p1

c

For how many of the following molecules does the bond order decrease if you add one electron to the neutral molecule? B2 C2 N2 F2 (question 3 M3V2)

2

What is the hybridization of the carbon atoms from left to right in the following molecule? (question 23 M3V1) a. sp, sp, sp b. sp2, sp2, sp2 c. sp2, sp, sp2 d. sp3, sp2, sp3

c

How many of the carbon atoms in the following molecule are characterized by sp hybridization? (question 25 M3V3) a. 0 b. 1 c. 2 d. 3

1

How many sigma bonds are found in CH2CHCH2NH2? a. 7 b. 9 c. 10 d. 11

10

The Lewis structure for molecule below has _____ σ bonds and ______ π bonds. (question 19 M3V2)

13, 3

Mendeleev's periodic table was proposed in 1869. However, many of the elements on the current periodic table were unknown to chemists of his time. Which of the following elements was on Mendeleev's periodic table? Ag Ne Rb U

Ag

Which species has the largest F-A-F bond angle, where A is the central atom? BF3 CF4 NF3 OF2

BF3

Which species has the largest ionization energy? F− Be2+ B N

Be2+

The dipole moment of ClF is 0.88 D. The dipole moment of BrF is 1.42 D. Statements I and II are both true. Which statement(s) explain(s) why BrF has the larger dipole moment? I. Br is larger than Cl. II. Br is less electronegative than Cl.

Both I and II

Which bond exhibits the most covalent character? C-H C-O Na-Cl B-F

C-H

Identify the figure showing the successive ionization energies of Mg. (question 26 M3V1)

Figure 2

What is the dominant Lewis structure for SCN−? (look at question 21 M3 V1)

I

Which Lewis structure (formal charges are not indicated) is dominant for the azide ion, N3−? (question 18 M3V2)

I

Which is a resonance form of the Lewis structure provided in the box below: (question 28 M3V3)

I

Which molecule(s) violate(s) the octet rule? I. NO II. SF2

I

Which one(s) of the following reactions will produce an ionic product with cation and anion ratio of 1:1? I. Na(s) + H2O(l) → ? II. Mg(s) + Br2(l) → ?

I

A potential energy diagram is shown below. Which atoms or ions might be represented in the diagram? I. He + He II. H + H III. Na+ + Na+ (question 9 M3V2)

I and III

According to MO theory and using the diagrams as needed in the provided information section, which molecule(s) is(are) paramagnetic? I. N2+ II. O22− (question 34 M3V3)

I only

Which of the following compounds have a linear shape? I. I3- II. O3

I only

These figures depict molecular orbitals formed by the overlap of 2p atomic orbitals. For a nitrogen molecule in the ground state, which of these molecular orbitals is(are) occupied by electrons? (question 34 M3V2)

II

Which of the following has resonance structures? (question 2 M3V2)

II

Which of the following molecules has(have) a non-zero dipole moment? I. CO2 II. CH2Cl2

II

Using the simple method of estimating Zeff (using Zeff = Z - S), what changes moving from boron to aluminum with respect to the outermost valence electron? I. The effective nuclear charge (Zeff) increases. II. The shielding increases.

II only

Which of the following Lewis structures is(are) valid? (question 22 M3V2)

II only

Which one of the following statements is(are) true? I. The first ionization energy of a K atom is larger than that of a Ca atom. II. The second ionization energy of a K atom is larger than that of a Ca atom.

II only

Place the following atoms/ions (Na+, Na, Mg2+) in order by increasing size.

Mg2+ < Na+ < Na

What is the electron configuration of the iron(II) cation?

[Ar]3d6

Arrange the following ionic compounds in order of decreasing magnitude of lattice energy? a. NaCl > RbBr > CsBr b. RbBr > CsBr > NaCl c. CsBr > RbBr > NaCl d. CsBr > NaCl > RbBr

a

Mendeleev predicted several properties of "Eka-Silicon," which is now known as Germanium. Which one of the following properties was Mendeleev unable to predict because it was not known during his time? a. atomic number b. atomic weight c. formula of oxide d. density

a

The S2N2 molecule is a cyclic structure with alternating S and N atoms. After accounting for the resonance structures shown in the figure, what is true regarding the S2N2 molecule? a. all bond lengths are equal b. one bond is shorter than the other 3 c. all four atoms have the same formal charge d. the internal bond angles are all exactly 109.5

a

The effective nuclear charge (Zeff ) increases slightly moving down a column. Why? a. A larger core electron cloud is less effective screening valence electrons. b. The number of protons increases as the atomic number increases. c .The core electrons move closer to the nucleus as the nuclear charge increases. d. The total mass of the nucleus increases as the nuclear charge increases.

a

Based on MO Theory and using the diagrams as needed in the provided information section, which of the following molecules/ions would have the smallest bond order? (question 19 M3V3) a. F2 b. F2− c. O2 d. O2−

b

Consider the following electron affinity data for fluorine and chlorine: F(g) + e - → F -(g) ΔE = -328 kJ/mol Cl(g) + e - → Cl -(g) ΔE = -349 kJ/mol What might explain why the value for chlorine is more exothermic? a. The average distance between the nucleus and the electron is larger for chlorine. b. Compared to fluorine, the electron-electron repulsions for chlorine are reduced. c. Ar is more stable than Ne, so it is more favorable to achieve this electron configuration. d. Fluorine is a more electronegative atom than chlorine.

b

Given the complete Lewis structure, what set of hybrid orbitals overlap to form the bond indicated by the arrow? (question 13 M3V3) a. sp3 and sp3 b. sp2 and sp3 c. sp2 and sp2 d. sp and sp3

b

Identify the pair with the same molecular geometry. a. BF3 and NH3 b. NH4+ and CH4 c. SO3 and SO32- d. CO2 and SO2

b

The ionization energies of which element are most consistent with the following data? (question 16 M3V3) a. Na b. Mg c. Li d. Si

b

The pi bond between the two carbon atoms in ethylene (C2H4) is formed because of an overlap between __________. a. two 2s orbitals b. two 2p orbitals c. two sp2-hybridized orbitals d. a 2p and a sp2-hybridized orbital

b

What is the hybridization of the bolded nitrogen and carbon atoms in the structure below? a. N = sp; C = sp2 b. N = sp2; C = sp2 c. N = sp; C = sp3 d. N = sp2; C = sp3 (question 14 M3V2)

b

Which bond is the least polar? a. C−F b. C−O c. Si−F d. Si-O

b

Which of the following oxides is the most basic? a. aluminum oxide b. potassium oxide c. silicon oxide d. sulfur trioxide

b

According to MO theory and using the diagrams as needed in the provided information section, which molecule(s) is(are) diamagnetic? I. N22+ II. O22− (question 17 M3V2)

both

Which of the following molecules is(are) polar? I. SF2 II. SF4

both

Considering the molecular orbital diagram of nitrogen monoxide, how is the NO bond influenced when an electron is removed? I. The bond order increases. II. The bond enthalpy increases. (question 16 M3V2)

both I and II

Given the following average bond enthalpy values for bonds between oxygen atoms (O-O = 146 kJ/mol; O=O = 495 kJ/mol), what are the expected bond enthalpy values for O3? a. less than 146 b. 146 c. between 146 and 495 d. 495 e. greater than 495

c

Identify the molecule with the largest dipole moment. a. CF4 b. BF3 c. IF3 d. SiH4

c

The bond enthalpy of C-H is 414 kJ/mol and C-Br is 285 kJ/mol. Which reaction is the most exothermic? a. CH4(g) → C(g) + 4 H(g) b. CBr4(g) → C(g) + 4 Br(g) c. C(g) + 4 H(g) → CH4(g) d. C(g) + 4 Br(g) → CBr4(g)

c

The first ionization energies of elements in the third row of the periodic table are shown below. Why is the I1 of S less than that of P? a. the zeff of s is less than that of p b. the radius of s is greater than that of p c. the additional electron in S fills an orbital leading to electron repulsion. d. the additional electron in S occupies a higher energy subshell.

c

Among the non-radioactive noble gases, Xe is the most likely to bond with other elements. Why? a. Xe has the most positive electron affinity. b. Xe has the most negative electron affinity. c. Xe has the greatest ionization energy. d. Xe has the lowest ionization energy.

d

For the partial Lewis structure below, fill in the missing lone pair(s). What is the formal charge on the sulfur atom in the resulting structure? (question 17 M3V3) a. -2 b. +2 c. +3 d. 0

d

What is the electron configuration of V3+? a. [Ar]4s2,3d10 b. [Ar] 4s2 c. [Ar]4s1, 3d1 d. [Ar]3d10

d

Which set is expected to show the smallest difference in first ionization energy? a. He, Ne, Ar b. B, N, O c. Mg, Mg+, Mg2+ d. Fe, Co, Ni

d

The darker dashed line in the figure represents the energetics accompanying the formation of a C-C single bond as atomic orbitals overlap. (question 33 M3V1)

figure c

According to MO theory, which molecule(s) is(are) paramagnetic? I. C2 II. O2 (question 34 M3V1)

only II