CHEM 10113, Exam 3 Name November 2, 2011 (please...

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CHEM 10113, Exam 3 Name_____________________ November 2, 2011 (please print)

All equations must be balanced and show phases for full credit. Significant figures count, and box your answers!

1. (11 points) In each blank write >, < or = as appropriate.

Cl-Cl bond polarity = H-H bond polarity

# of valence electrons in SeO2

= # of valence electrons in NO2

–

EA of Ta < EA of Cu

electronegativity of Re < electronegativity of Ru

size of Kr > size of Rb+

IE of Sr < IE of Sr+

Bond order of O2 > Bond order of F2

Wavelength of IR light > Wavelength of X-rays

Energy of blue light > Energy of orange light

2. (12 points) Briefly define the following terms. Shielding – screening of one electron from the nuclear charge by other electrons around the same atom Free radical – An atom or molecule containing an unpaired electron Covalent bond – An interatomic attraction resulting from the sharing of electrons between atoms Expanded octet – In a Lewis structure, when the central atom of a molecule bears more than 8 electrons, occurs for 3rd row or higher (hypervalency) 3. (10 points) SHOW ALL WORK. Use tabulated average bond energies (appended to exam) to estimate the enthalpy of the following reaction. H2O2(g) H2O(g) + ½ O2(g)

+ ½

Hrxn = [H bonds broken] - [H bonds formed]

Hrxn = [2(O-H) + (O-O)] – [2(O-H) + 1/2(O=O)]

Hrxn = [2(464 kJ/mol) + 142 kJ/mol] – [1/2(498 kJ/mol) + 2(464 kJ/mol)]

Hrxn = -107 kJ/mol

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4. (15 pts) SHOW ALL WORK. A heat lamp produces 32.8 watts of power at a

wavelength of 6.5 m. How many photons are emitted per second? (1 watt = 1 J/s) 32.8 watts 1 J/s = 32.8 J/s 1 watt

= 6.5 m 10-6 m = 6.5 x 10-6 m

1 m

= c = 2.998 x 108 ms-1 = 4.61 x 1013 s-1

6.5 x 10-6 m

E=h = (6.626x10-34 J s/photons)(4.61 x 1013 s-1) = 3.05 x 10-20 J/photon 32.8 J x photons = 1.1 x 1021 photons/s s 3.05 x 10-20 J 5. (3 points) If the value of ml for an electron in an atom is –3, what is the smallest value of l that the electron could have? ml = -3; l= 3 6. (2 point) Which quantum number is related to shape of the orbital?

Shape l

7. (12 points) Fill in the blanks in the following equations. For coefficients of 1, please write “1” rather than leaving blank. Example: __ MgCl2(___) + __ AgNO3(___) __ ____(s) + 1 ______(___) Answer: 1 MgCl2(aq) + 2 AgNO3(aq) 2 AgCl(s) + 1 Mg(NO3)2(aq)

a) _1__ __I2___ ( s ) + __Pt__ ( s ) _1_ PtI2( s )

b) _1_ H2( g ) + F2( g ) _2__ __HF__ (g)

8. (6 points) Name the element or ion:

a. Its valence electron configuration is ns1 and its most stable ion has the same electron configuration as krypton.__Rb____ b. It has 7 unpaired valence electrons and is a lanthanide.__Eu___ 9. (6 points) Give the complete electron configuration for a. P2– ion, and b. Be. a) P2- : 1s22s22p63s23p5

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b) Be: 1s22s2 10. (5 points) Write the standard formation reaction for Cu(NO3)2·3H2O(s).

Cu(s) + N2(g) + 9/2 O2(g) + 3 H2(g) Cu(NO3)2·3H2O(s) 11. (6 points) Give the short-hand electron configurations for a. Co+, and b. Pb. a) Co+: [Ar]3d8

b) Pb: [Xe]6s24f145d106p2 12. (6 points) Give the valence electron configurations of a. Ge, and b. Eu. a) Ge: 4s24p2

b) Eu: 6s24f7 13. (6 points) Write the chemical equations for a. the second ionization energy of zinc, and b. the EA of Y.

a) Zn+ (g) Zn 2+

(g) + e-

b) Y(g) + e- Y-(g)

14. (6 points) Contrast three properties of alkali metals and three properties of the noble gases.

Alkali metals Noble gases

Easily reactive w/halogens Non-reactive

Metallic/ high mp, bp

Nonmetals/ low mp, bp

Low IE

High IE

15. (3 points) The bond order of the N-O bond in NO2

− is ___1.5____.

16. (10 points) SHOW ALL WORK. Calculate the enthalpy change for the reaction

Ca2+(aq) + 2 OH–

(aq) + CO2(g) CaCO3(s) + H2O(l) by manipulating the following equations.

FLIP [CaCO3(s) CaO(s) + CO2(g)] H = [–178.1 kJ] FLIP

FLIP [CaO(s) + H2O(l) Ca(OH)2(s)] H = [–65.3 kJ] FLIP

FLIP [Ca(OH)2(s) Ca2+(aq) + 2 OH–

(aq)] H = [–16.2 kJ] FLIP

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Perform the manipulations to receive the following equations:

CO2(g) + Ca(s) CaCO3(s) H = +178.1 kJ

Ca(OH)2(s) CaO(s) + H2O(g) H = + 65.3 kJ

Ca2+(aq)

+ 2 OH –(aq) Ca(OH)2 (s) + H = +16.2 kJ +259.6 kJ 17. (24 points) Write the complete Lewis electron dot formulas for each of the molecules below. Please put the final answers in the boxes; anything outside of the boxes will not be graded. Formal Charge = (# of valence e– in the isolated atom) - (# of bonds to the atom) - (# of unshared electrons on the atom) O2

2–

NF3

ClO3–

<-> <->

PCl4+

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18. (7 points) SHOW ALL WORK. Use the Born-Haber cycle as shown to

determine the value of H for step 3.

-411 kJ

+108 kJ

+122 kJ

-349 kJ

-788 kJ

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Hf = H step 1 + H step 2 + H step 3 + H step 4 + H step 5

-411 = 108 + 122 + H step 3 + -349 + -788

H step 2 = 496 CHEM 10113, Exam 3 Name_____________________ November 2, 2011 (please print)



IE of Ca+ < IE of Ca2+

# of valence electrons in OCN–

< # of valence electrons in NO2

–

polarity of Sb-Cl bond

> polarity of Cl-Cl bond

Frequency of radiowaves < Frequency of UV light

Bond order of CO = Bond order of N2

Size of S2– ion > Size of Ar ion

EA of In > EA of Hf

electronegativity of I > electronegativity of Au

Wavelength of gamma rays

< Wavelength of X-rays

2. (12 points) Briefly define the following terms. Diamagnetic – Repelled by a magnetic field, having all paired electrons Ionic bond – The electrostatic attraction between a positive and a negative ion resulting from complete transfer of one or more electrons from one atom to another Emission spectrum – Spectrum of frequencies of electromagnetic radiation emitted by an atom or molecule when it relaxes to a lower energy state Ground state – The state of an atom or molecule in which all electrons are in the lowest possible energy levels 3. (10 points) SHOW ALL WORK. Use tabulated average bond energies (appended to exam) to estimate the enthalpy of the following reaction. Cl2CF2(g) + F2(g) CF4(g) + Cl2(g)

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+ +

H rxn = [H bonds broken] - [H bonds formed]

H rxn = [2(C-F) + 2(C-Cl) + (F-F)] – [4(C-F) + (Cl-Cl)]

H rxn = [2(485 kJ/mol) + 2(339 kJ/mol) + 159 kJ/mol] – [4(485 kJ/mol) + (243

kJ/mol)]

H rxn = -376 kJ/mol

4. (15 pts) SHOW ALL WORK. A heat lamp produces 34.6 watts of power at a


= 5.5 m 10-6 m = 5.5 x 10-6 m

1 m

= c = 2.998 x 108 ms-1 = 5.45 x 1013 s-1

5.5 x 10-6 m

E=h = (6.626x10-34 J s/photons)(5.45 x 1013 s-1) = 3.61 x 10-20 J/photon 34.6 J x photons = 9.6 x 1020 photons/s s 3.61 x 10-20 J 5. (3 points) If the value of ml for an electron in an atom is –3, what is the smallest value of n that the electron could have? ml = -3; n= 4 6. (2 point) Which quantum number is related to spatial orientation?

Spatial orientation ml

7. (12 points) Fill in the blanks in the following equations. For coefficients of 1, please write “1” rather than leaving blank. Example: __ MgCl2(___) + __ AgNO3(___) __ ____(s) + 1 ______(___) Answer: 1 MgCl2(aq) + 2 AgNO3(aq) 2 AgCl(s) + 1 Mg(NO3)2(aq)

a) _1__ __Cl2___ ( g ) + __Zn___ ( s ) _1__ ZnCl2( s )

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b) _1__ I2( s ) + F2( g ) _2__ _IF___ (g)


a. Its electron configuration is 1s22s22p1 and it has a +1 charge.__C+___ b. It has 5 unpaired valence electrons and its highest principle level is 6._Re___ 9. (6 points) Give the complete electron configurations for a. Si+ ion, and b. C. a) Si+: 1s22s22p63s23p1 b) C: 1s22s22p2 10. (5 points) Write the standard formation reaction for MgSO4·7H2O(s).

Mg(s) + S(g) + 11/2 O2(g) + 7 H2(g) MgSO4·7H2O(s) 11. (6 points) Give the short-hand electron configurations for a. Os+, and b. Te. a) Os+: [Xe]4f145d7 b) Te: [Kr]5s24d105p4 12. (6 points) Give the valence electron configurations of a. Sn, and b. Nd. a) Sn: 5s25p2 b) Nd: 6s24f4 13. (6 points) Write the chemical equations for a. the second ionization energy of cadmium, and b. the EA of Db.

a) Cd+(g) Cd2+

(g) + e-

b) Db(g) + e- Db-

(g) 14. (6 points) Contrast three properties of alkali metals and three properties of the halogens.

Alkali metals halogens

Easily oxidized Easily reduced

Low EA High EA

Low IE High IE

15. (3 points) The bond order of the P-O bond in PO4

3− is ___1.25____. 16. (10 points) SHOW ALL WORK. Calculate the enthalpy change for the reaction

C(s) + 2 H2(g) CH4(g) by manipulating the following equations.

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C(s) + O2(g) CO2(g) H = –393.5 kJ

x2[ H2(g) + ½ O2(g) H2O(l) ] H = [–285.8 kJ] x2

FLIP [ CH4(g) + 2 O2(g) CO2(g) + 2 H2O(l)] H = [–890.3 kJ] FLIP Perform manipulations to receive the following equations:

C(s) + O2(g) CO2(g) H = –393.5 kJ

2 H2(g) + O2(g) 2 H2O(l) H = –571.6 kJ

CO2(g) + 2 H2O(l) CH4(g) + 2 O2(g) H = +890.3 kJ -74.8 kJ 17. (24 points) Write the complete Lewis electron dot formulas for each of the molecules below. Please put the final answers in the boxes; anything outside of the boxes will not be graded. Formal Charge = (# of valence e– in the isolated atom) - (# of bonds to the atom) - (# of unshared electrons on the atom) NO–

IF4–

NO3

–

10

<-> <->

CCl4



-411 kJ

+108 kJ

+122 kJ

+496 kJ

-788 kJ

11


-411 = 108 + 122 + 496 + H step 4 + -788

H step 2 = -349 CHEM 10113, Exam 3 Name_____________________ November 2, 2011 (please print)



bond order of F2 < bond order of N2

EA of V < EA of Zn

of microwaves > of yellow light

electronegativity of P > electronegativity of Mg

size of Br– > size of Kr

IE of Ar– < IE of Ar

Energy of radiowaves < Energy of microwaves

C=O bond polarity > H-H bond polarity

# of valence electrons in H2CO2

< # of valence electrons in Cl2CO

2. (12 points) Briefly define the following terms. Effective nuclear charge – The positive charge experienced by an electron in a multielectron atom, when taking shielding into account Electron sea model – Model of metallic bonding in which cations are considered to be fixed points within a mobile “sea” of electrons degenerate – of equal energies Paramagnetic – Attracted by a magnetic field, having unpaired electrons 3. (10 points) SHOW ALL WORK. Use tabulated average bond energies (appended to exam) to estimate the enthalpy of the following reaction. H2C=CH2(g) + Br2(g) BrH2C-CH2Br(g)

12

+

H rxn = [H bonds broken] - [H bonds formed]

H rxn = [(C=C) + (Br-Br)] – [2(Br-C) + (C-C)]

H rxn = [611 kJ/mol + 193 kJ/mol] – [2(285 kJ/mol) + 347 kJ/mol]

H rxn = -113 kJ/mol 4. (15 pts) SHOW ALL WORK. A heat lamp produces 40.0 watts of power at a


= 6.1 m 10-6 m = 6.1 x 10-6 m

1 m

= c = 2.998 x 108 ms-1 = 4.91 x 1013 s-1

6.1 x 10-6 m

E=h = (6.626x10-34 J s/photons)(4.91 x 1013 s-1) = 3.25 x 10-20 J/photon 40.0 J x photons = 1.2 x 1021 photons/s s 3.25 x 10-20 J 5. (3 points) If the value of ml for an electron in an atom is –4, what is the smallest value of n that the electron could have? ml = -4; n= 5 6. (2 point) Which quantum number is related to energy?

Energy n 7. (12 points) Fill in the blanks in the following equations. For coefficients of 1, please write “1” rather than leaving blank. Example: __ MgCl2(___) + __ AgNO3(___) __ ____(s) + 1 ______(___) Answer: 1 MgCl2(aq) + 2 AgNO3(aq) 2 AgCl(s) + 1 Mg(NO3)2(aq)

a) _2__ Li ( s ) + _2__ H2O(l) __H2___(g) + _2__ __LiOH___(aq)

b) _2__ __Cs__ ( s ) + Br2( l ) _2__ CsBr( s )

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a. Its electron configuration is 1s22s22p5 and it has a -1 charge. __O–___ b. It has 4 unpaired valence electrons and its highest principle level is 4.__Cr__ 9. (6 points) Give the complete electron configurations for a. Cl+ ion, and b. F. a) Cl+: 1s22s22p63s23p4 b) F: 1s22s22p5 10. (5 points) Write the standard formation reaction for CuSO4·5H2O(s).

Cu(s) + S(g) + 9/2 O2(g) + 5 H2(g) CuSO4·5H2O(s) 11. (6 points) Give the short-hand electron configurations for a. Au+, and b. Po. a) Au+: [Xe]4f145d10

b) Po: [Xe]6s24f145d106p4 12. (6 points) Give the valence electron configurations of a. Pb, and b. Ce. a) Pb: 6s26p2 b) Ce: 6s24f15d1 13. (6 points) Write the chemical equations for a. the second ionization energy of mercury, and b. the EA of Re.

a) Hg+(g) Hg2+

(g) + e-

b) Re(g) + e- Re-(g)

14. (6 points) Contrast three properties of halogens and three properties of the noble gases.

halogens Noble gases

Diatomics in nature Not diatomics

High EA Low EA

Very reactive Non-reactive

15. (3 points) The bond order of the C-O bond in HCO2

− is ___1.5______. 16. (10 points) SHOW ALL WORK. Calculate the enthalpy change for the reaction

2 HCl(g) + F2(g) 2 HF(l) + Cl2(g) by manipulating the following equations.

X1/2 [4 HCl(g) + O2(g) 2 H2O(l) + 2 Cl2(g) ] H = [–202.4 kJ] x1/2

X2 [½ H2(g) + ½ F2(g) HF(l) ] H = [–600.0 kJ] x2

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FLIP [H2(g) + ½ O2(g) H2O(l)] H = [–285.8 kJ] FLIP Perform manipulations to give the following equations:

2 HCl(g) + ½ O2 (g) H2O(l) + Cl2(g) H = -101.2 kJ

H2(g) + F2(g) 2HF(l) H= -1200.0 kJ

H2O H2(g) + ½ O2(g) + H= +285.8 kJ -1015.4 kJ 17. (24 points) Write the complete Lewis electron dot formulas for each of the molecules below. Please put the final answers in the boxes; anything outside of the boxes will not be graded. Formal Charge = (# of valence e– in the isolated atom) - (# of bonds to the atom) - (# of unshared electrons on the atom) BrO–

ClO4

–

<-> <-> <->

15

SBr2

AsCl4+



+108 kJ

+496 kJ

-349 kJ

-788 kJ

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-411 = 108 + H step 2 + 496 + -349 + -788

H step 2 = 122

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