Chem 1412-82005 Chemistry: Spring-2021 Final Exam Answers

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Your Name:
­­­­­­______
Total Points = 80


Submit on eCampus by 11:59 PM, Thursday, 05/13/2021.

Multiple-Choice Questions

Select one correct answer in each of the following questions.

Group A (1 × 18 = 18 Points)

Which of these compounds has the lowest viscosity as a liquid?
CH3CH2CH2CH3
CH3CH2NH2
CH3OCH3
CH3Cl
CH3CH2OH

The predominant intermolecular attractions between molecules of fluoropropane, CH3CH2CH2F, are:
ion-dipole.
dipole-dipole forces.
dispersion forces.
hydrogen bonds.
covalent bonds.

For which of the following reactions will a change in the pressure will not affect the value of Q?
A(g) ⇌ B(g)
2 A(g) ⇌ B(g)
A(g) ⇌ 2 B(g)
2 A(s) ⇌ B(l)
a and d only

Which solution has the highest pH?
050 M HNO2,
050 M HClO2,
050 M HIO3,
050 M HIO4,
010 M HNO2,

Select the Lewis acid and Lewis base in this reaction. 6 H2O(l) + Co3+(aq) → Co(H2O)63+(aq)
H2O is the Lewis base, but there is no Lewis acid.
Co3+ is the Lewis acid, and H2O is the Lewis base.
H2O is the Lewis acid, and Co3+ is the Lewis base.
Co3+ is the Lewis acid, and there is no Lewis base.
None of the above is correct.

Which species could form a buffer when combined with H2PO4−?
either H3PO4 or HPO42−
either HPO42− or PO43−
either H3PO4 or PO43−
PO43− only
H2PO4− only

Select the situation in which a process is not
DSsys and DSsurr are both positive.
DSsys and DSsurr are both negative.
DSsys is negative, but there is a larger, positive change in DSsurr.
DSsurr is negative, but there is a large, positive change in DSsys.
The process is spontaneous in all of the above scenarios.

Select the scenario in which the equilibrium constant of a reaction is K > 1.
< 0

0
= 0
DG < 0 DG > 0

Select the best description for the following this reaction: Cu2O(s) + 2 H+(aq) → Cu(s) + Cu2+(aq) + H2O(l)
Copper undergoes an oxidation reaction.
Copper undergoes a reduction reaction.
Copper undergoes a decomposition reaction.
Copper(II) undergoes a redox reaction.
Copper(I) undergoes a disproportionation reaction.

Which statement is incorrect for the term nuclear magic number?
These are the number of electrons needed to fill each main energy level.
These are numbers of protons associated with stable nuclei.
These are numbers of neutrons associated with stable nuclei.
These numbers are responsible for the existence of non-radioactive isotopes.
Magic numbers for protons are 2, 8, 20, 28, 50, or 82 and magic numbers for neutrons are 2, 8, 20, 28, 50, 82, or 126.

Which statement describes correctly the following nuclear reaction?
3He + ? → 4He + 1H

nuclear fusion reaction with missing reactant hydrogen-2
nuclear fission reaction with missing reactant hydrogen-2
nuclear fusion reaction with missing reactant helium-2
nuclear fission reaction with missing reactant helium-2
nuclear fusion reaction with missing reactant helium-3

Name the following compound:
1,1-dimethyl-3-ethylpentane
4-ethyl-2-methylhexane
3-ethyl-5-methylhexane
3-ethyl-4-isopropylbutane
Nonane

Select the false statement about benzene.
It is a saturated hydrocarbon.
It is an aromatic hydrocarbon.
Its carbon atoms follow the octet rule.
It has a planar (flat) structure.
It contains delocalized electrons.

What is the oxidation state of the transition metal in Na2WO4?
+1
+2
+8
+6
+5

The reaction A + 3 B → Products has an initial rate of 0.0345 M/s and the rate law rate = k[A]2[B]. What will the initial rate be if [A] is quadrupled and [B] is halved?
069 M/s
138 M/s
276 M/s
552 M/s
10 M/s

For the reaction 2 A → B + 3 C, the rate of change of A is . What is the corresponding rate of change of C?

What type of octahedral complex is paramagnetic when high spin but diamagnetic when low spin?

Consider the following reaction, for which Kc = 0.0136 at 731 K.

Which statement is always true, regardless of the conditions (temperature, pressure, etc.)?

Kc = 0.0136
Kp = 0.0136
Kc = Qc
Kp = Qp
Kp = Kc

Group B (2 × 5 = 10 Points)

You need to show your works completely and clearly to receive full credits.

Determine the freezing point of KCl solution in water. The freezing point depression constant, Kf, of water is 1.86 °C/m. Molality of KCl is 0.350 m.
651 °C
–0.651 °C
12 °C
–1.30 °C
–1.95 °C

A solution contains 0.125 mol sucrose dissolved into 1.545 mol ethanol. What is the vapor-pressure lowering, ΔP, of this solution? The vapor pressure of ethanol is 0.0772 atm at 298 K.
001217 atm
002803 atm
005776 atm
0163 atm
0714 atm

Calculate Kp for the following reaction at 300 K if the equilibrium pressures are , , and .
378
83
0120
00265
4

Calculate the pH of a buffer containing 0.135 M HA (HA is a weak acid with ) and 0.225 M KA.
67
53
41
97
34

Calculate the standard potential for the voltaic cell constructed from the following half-cells:
Sn(s) → Sn2+(aq) + 2e

Ag+(aq) → Ag(s) – e

66 V
74 V
94 V
−0.66 V
46 V

Free-Response Questions

Show your works completely and clearly to receive full credits.

(2+4 = 6 points)
Following diagram represents a unit cell of a metal. What type of unit cell is it? sc, bcc, or fcc? How many atoms per unit cell does this metal contain? Justify.

Nickel with atomic radius 6 pm consists of face-centered cubic unit cells. Calculate the density of nickel.

(1+4 = 5 Points)
Determine the van’t Hoff factor for (NH4)3PO4 assuming 100% dissociation.
Determine the osmotic pressure of a 0.0150 M solution of MgCl2 at 25 °C (a) assuming 100% dissociation of the salt and (b) given a van’t Hoff factor of 2.68.
The complexes of the type [PdX2Y2] are well-known compounds in coordination chemistry.
Draw the structures of cis and trans isomers of [PdX2Y2].
What is the coordination number of Pd in this coordination compound? (2+1 = 3 Points)

You have an octahedral coordination compound [MY6] which is a low-spin d6
Show the distribution of electrons in in the t2g d-orbitals and eg d-orbitals by drawing crystal field splitting diagram.
Is this compound diamagnetic or paramagnetic? Why? (2+2 = 4 Points)
The reaction between Fe(NO3)3 and KSCN was carried out and the net ionic reaction for this reaction is as following:
Fe3+(aq) + SCN–(aq) ⇌ Fe(SCN)2+(aq)

                                    (yellow)      (colorless)         (red)

Giving a suitable reason, write whether the intensity of redness increases or decreases after adding:

aqueous FeCl3
aqueous AgNO3 (4 Points)
Split the following redox reaction into oxidation half and reduction half reactions, balance the half reactions (both charges and atoms), and write the balanced overall reaction. Show all steps. Identify the oxidizing agent and reducing agent in this reaction. (4+1 = 5 Points)
Ag + MnO4– + H+ → Mn2+ + Ag+ + H2O

Based on the ionic concentrations given below, calculate the ionic product (Q) and predict whether each of the following sparingly soluble salt will precipitate from the solution. (5 Points)
PbI2: [Pb2+] = 0.0013 M, [I–] = 1.5 × 10–3 M (Ksp = 1.4 × 10–8)
Ag2S: [Ag+] = 1.0 × 10–15 M, [S2–] = 1.0 × 10–17 M (Ksp = 1.6 × 10–49)

Find the pH of 0.250 M solution of NaOI (For HOI, . (5 Points)

Consider the combustion of benzene, C6H6.

Using the following thermochemical data at 25 °C to determine

standard free energy change for the reaction ()
Equilibrium constant (Kc) (5 Points)

Species (kJ/mol) (J/mol×K)
C6H6(l) 49.1 173.4
O2(g) 0 205.2
CO2(g) −393.5 213.8
H2O(g) −241.8 188.8

(4+2 = 6 Points)
The rate constant for a first-order reaction is . If one-quarter of a radioactive sample remains after 2.00 hours, what is the rate constant of its decay reaction?
Pt-200 isotope undergoes beta decay. Write the nuclear equation for this radioactive decay.
(4 Points)

Name the following two compounds:

Label the following two compounds as an alcohol or an ether:

CH3–CH2–O–CH2–CH2–CH2–CH3

(2+5 = 7 Points)
The rate law for a reaction is as shown below:
Rate = k [A]2[B]

By what factor does the rate increase or decrease for the gaseous reaction if:

Partial pressure of A is doubled while that of B is kept constant?
Partial pressure of A is kept constant and that of B is doubled?
Remember, partial pressure for a gaseous reaction is equivalent to concentration.

Determine the rate law and find the value of rate constant (with its unit) for the following reaction given the initial rate data in the table:
2 A + 2 B → C + 2 D

Experiment A B Initial rate (M/s)
1 0.0422 0.113
2 0.0844 0.113
3 0.0844 0.226

Reference Materials

Simple cubic unit cell:

Body-centered cubic unit cell:

Face-centered cubic unit cell:

Quantity c, H2O(s) c, H2O(l) c, H2O(g) ∆Hfus H2O ∆Hvap H2O
Value

Zero order First order Second order

Strong acids: HCl, HBr, HI, HNO3, H2SO4, HClO4, HClO3

Strong bases: LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

For the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g)

(P = Partial pressure)

For more examples on the reactions involving solid, liquid, gas, or aqueous species, see the eBook or video on discussion board.

Avogadro’s number (NA) = 6.022 × 1023 /mol

1 pm = 10-10 cm = 10-12 m

For an isothermal process,

At constant pressure,

T

Depending on the reaction situation:

Ka (If a Bronsted-Lowry acid is a reactant)

Kb (If a Bronsted-Lowry base is a reactant)

  (here, refers to standard reduction potential, )

Half-reaction
(volts)
Co3+(aq) + e− → Co2+(aq) 1.92
MnO4−(aq) + 8 H+(aq) + 5 e− → Mn2+(aq) + 4 H2O(l) 1.51
Br2(l) + 2 e− → 2 Br−(aq) 1.07
Ag+(aq) + e− → Ag(s) 0.80
Fe3+(aq) + e− → Fe2+(aq) 0.77
Ni(OH)2(s)+ 2 e– → Ni(s) + 2 OH−(aq) 0.72
Cu2+(aq) + 2 e− → Cu(s) 0.34
2 H+(aq) + 2 e− → H2(g) 0.00
Pb2+(aq) + 2 e− → Pb(s) −0.13
Sn2+(aq) + 2 e− → Sn(s) −0.14
Cd2+(aq) + 2 e− → Cd(s) −0.40
Cr3+(aq) + e− → Cr2+(aq) −0.41
Fe2+(aq) + 2 e− → Fe(s) −0.44
Cr3+(aq) + 3 e− → Cr(s) −0.74
Cd(OH)2(s) + 2 e− → Cd(s) + 2 OH−(aq) −0.81
Ti2+(aq) + 2 e− → Ti(s) −1.63
Al3+(aq) + 3 e− → Al(s) −1.66
Mg2+(aq) + 2 e− → Mg(s) −2.38
Ba2+(aq) + 2 e− → Ba(s) −2.91
K+(aq) + e− → K(s) −2.93

Particle Mass (u)
Proton 1.00728
Neutron 1.00866
Electron 0.00055

prefix meth eth prop but pent hex hept oct non dec

C 1 2 3 4 5 6 7 8 9 10

Molecule or ion Ligand name Coordination Donor atom(s)
NH3 Ammine Monodentate N
H2O Aqua Monodentate O
N3– Azido Monodentate N
Br− Bromido Monodentate Br
CO32– Carbonato Bidentate O and O
CO Carbonyl Monodentate C
Cl− Chlorido Monodentate Cl
CN− Cyanido Monodentate C
NH2CH2CH2NH2 (en) Ethylenediamine Bidentate N and N
EDTA4– Ethylenediaminetetraacetato Hexadentate Four O and two N
F− Fluorido Monodentate F
OH− Hydroxido Monodentate O
I− Iodido Monodentate I
NO2− Nitrito Monodentate N or O
C2O42– Oxalato Bidentate O and O
SCN– Thiocyanato Monodentate S or N

Splitting Diagrams

Spectrochemical Series

Strong-field ligands tend to produce low-spin complexes and weak-field ligands tend to produce high-spin complexes.

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