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Problem Set 6 on Inorganic Chemistry - Electrochemical Reactions | CHM 218, Assignments of Inorganic Chemistry

Material Type: Assignment; Professor: Berger; Class: Intro Inorganic Chem; Subject: Chemistry; University: Indiana University-Purdue University-Fort Wayne; Term: Spring 2006;

Typology: Assignments

Pre 2010

Uploaded on 08/18/2009

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Chemistry 218
Name_____________________________ Problem Set #6
This problem set is due by the end of class on Wednesday, April 20
th
. Please begin answering the
questions directly on this sheet and add as many additional sheets as necessary.
Where an explanation
is requested, the majority of the points depend on the explanation. For quantitative problems,
all work must be shown.
1. R-C&O 15.52
2. R-C&O 15.78
3. R-C&O 16.31
4. R-C&O 17.42 Contrary to what the book asks, you are actually supposed to use the data given to
calculate the bond Cl
!
Cl energy in Cl
2+
.
5. R-C&O 17.56
6. R-C&O 18.24
7. Given that the Xe
!
F bond energy is 133 kJ/mol, the F
!
F bond energy is 159 kJ/mol and that the
enthalpy of sublimation of XeF
4
is 62 kJ/mol, estimate
)
H
f
° of XeF
4
(s).
1.
½ N2 (g) + 3 H2O (R) + 3 e! (aq) 6 NH3 (aq) + 3 OH! (aq)
)G° = [1 mol ()G°
f (NH3 (aq))) + 3 mol ()G°
f (OH! (aq))) ]
! [½ mol ()G°
f (N2 (g)) + 3 mol ()G°
f (H2O (R)) + 3 mol ()G°
f (e! (aq)))]
)G° = [1 mol (!26.5 kJ @ mol!1) + 3 mol (!157 kJ @ mol!1)]
! mol (0 kJ @ mol!1) + 3 mol (!237 kJ @ mol!1) + 3 mol (0 kJ @ mol!1)] =
+214 kJ
)G° = !nFE°
pf3
pf4

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Chemistry 218 Name_____________________________ Problem Set # This problem set is due by the end of class on Wednesday, April 20th. Please begin answering the questions directly on this sheet and add as many additional sheets as necessary. Where an explanation is requested, the majority of the points depend on the explanation. For quantitative problems, all work must be shown.

  1. R-C&O 15.
  2. R-C&O 15.
  3. R-C&O 16.
  4. R-C&O 17.42 Contrary to what the book asks, you are actually supposed to use the data given to calculate the bond Cl! Cl energy in Cl 2 +^.
  5. R-C&O 17.
  6. R-C&O 18.
  7. Given that the Xe! F bond energy is 133 kJ/mol, the F! F bond energy is 159 kJ/mol and that the enthalpy of sublimation of XeF 4 is 62 kJ/mol, estimate ) H° of XeFf 4 (s).

1. ½ N 2 (g) + 3 H 2 O (R) + 3 e!^ (aq) 6 NH 3 (aq) + 3 OH!^ (aq)

)G° = [1 mol ()G°f (NH 3 (aq))) + 3 mol ()G°f (OH!^ (aq))) ]

! [½ mol ()G°f (N 2 (g)) + 3 mol ()G°f (H 2 O (R)) + 3 mol ()G°f (e!^ (aq)))]

)G° = [1 mol (!26.5 kJ @ mol!^1 ) + 3 mol (!157 kJ @ mol!^1 )]

! [½ mol (0 kJ @ mol!^1 ) + 3 mol (!237 kJ @ mol!^1 ) + 3 mol (0 kJ @ mol!^1 )] =

+214 kJ

)G° = !nFE°

N N

N

H

N N

N

H

N N

N

+1 H

O S O

O

O S O

O

O S O

O

-1 -1 -

O S O

O

O S O

O

-1 (^) +

O S O

O

+1^ -

O S O

O

  1. The second and third resonance structure are expected to be minor contributors at best. Therefore we expect the bond between the two N atoms not bonded to H to be significantly shorter than the N-N bonds involving the N atom bonded to H.
  2. The resonance structures with the most favorable formal charge distributions for sulfur trioxide and for the sulfite ion are shown. In sulfur trioxide the average

bond order is between 1 b and 2, while that in the sulfite ion is 1a. Therefore,

sulfur trioxide will have the stronger bonds. The S!O bond length in sulfur

trioxide is 142 pm, while that in the sulfite ion is 151 pm.

4. Cl 2 6 2 Cl^ )H = +240 kJ

Cl 6 Cl+^ + e!^ )H = +1250 kJ

Cl________________ 2 +^ + e!^6 Cl 2 ________________)H = !1085 kJ

Cl 2 +^6 Cl + Cl+^ )H = +405 kJ

The bond energy in Cl 2 +^ is greater than that in Cl 2 , consistent with the fact

that the electron that is lost comes out of a B* M.O.

7. For the gas phase reaction Xe (g) + 2 F 2 (g) ˜ XeF 4 (g)

)H. 2 mol (DF!F)! 4 mol (DXe!F)

)H. 2 mol (159 kJ/mol)! 4 mol (+133 kJ/mol) = !214 kJ

Xe (g) + 2 F 2 (g) ˜ XeF 4 (g) )H. !214 kJ

XeF 4 (g) ˜ XeF 4 (s) )H = !62 kJ

________________________ _____________

Xe (g) + 2 F 2 (g) ˜ XeF 4 (s) )H. !276 kJ