Cocomama123
Badges: 3
Rep:
?
#1
Report Thread starter 3 years ago
#1
Question from OCR A Student Book: 9.3 Summary Questions

Use Table 1 and the following data:

2SO2(g) + O2(g) → 2SO3(g) ΔH= -192kJmol-1

Assume that SO2 and SO3 contain only S=O bonds
a) Calculate the average bond enthalpy for the S=O bond.
b) The actual bond enthalpy for the S=O bond in SO2 is 531kJmol-1. Calculate the actual bond enthalpy for the S=O bond in SO3.

Table 1:
Name:  tabe 1.png
Views: 1136
Size:  49.1 KB
1
reply
MexicanKeith
Badges: 12
Rep:
?
#2
Report 3 years ago
#2
(Original post by Cocomama123)
Question from OCR A Student Book: 9.3 Summary Questions

Use Table 1 and the following data:

2SO2(g) + O2(g) → 2SO3(g) ΔH= -192kJmol-1

Assume that SO2 and SO3 contain only S=O bonds
a) Calculate the average bond enthalpy for the S=O bond.
b) The actual bond enthalpy for the S=O bond in SO2 is 531kJmol-1. Calculate the actual bond enthalpy for the S=O bond in SO3.

Table 1:
Name:  tabe 1.png
Views: 1136
Size:  49.1 KB
What have you tried/what specifically is causing trouble in answering this question?
0
reply
Cocomama123
Badges: 3
Rep:
?
#3
Report Thread starter 3 years ago
#3
(Original post by MexicanKeith)
What have you tried/what specifically is causing trouble in answering this question?
By using the equation, I found that 2SO2 has 4(S=O) bonds, O2 has 1 (O=O) and 2SO3 has 6 (S=O),
Since (O=O) is 498 and the Enthalpy change is -192
I set up an equation:
4(S=O) + (O=O) —> 6(S=O)
4(S=O) + 498 – 6(S=O) = –192kJmol-1

By rearranging:
690 = 2(S=O)
345 = (S=O)

However the answer to the questions in the book is 469 which doesn't show working out. I know the book has many mistakes with answers so I'm not sure if I'm completely off the mark or if there's something wrong with the books answer.

Since I'm not sure about question a, I really don't know how to go about answering b)
0
reply
charco
Badges: 17
Rep:
?
#4
Report 3 years ago
#4
(Original post by Cocomama123)
By using the equation, I found that 2SO2 has 4(S=O) bonds, O2 has 1 (O=O) and 2SO3 has 6 (S=O),
Since (O=O) is 498 and the Enthalpy change is -192
I set up an equation:
4(S=O) + (O=O) —> 6(S=O)
4(S=O) + 498 – 6(S=O) = –192kJmol-1

By rearranging:
690 = 2(S=O)
345 = (S=O)

However the answer to the questions in the book is 469 which doesn't show working out. I know the book has many mistakes with answers so I'm not sure if I'm completely off the mark or if there's something wrong with the books answer.

Since I'm not sure about question a, I really don't know how to go about answering b)
You have calculated it correctly.
1
reply
Cocomama123
Badges: 3
Rep:
?
#5
Report Thread starter 3 years ago
#5
(Original post by charco)
You have calculated it correctly.
Wow
Thank you so much,
Do you have any idea about question b)
0
reply
MexicanKeith
Badges: 12
Rep:
?
#6
Report 3 years ago
#6
(Original post by Cocomama123)
Wow
Thank you so much,
Do you have any idea about question b)
As charco said your calculation is correct for part a

for part b you can use the equation you have written down, but now you have to treat the S=O bonds in SO2 and SO3 as different.

so

4(S=O)SO2 + 498 – 6(S=O)SO3 = –192kJmol-1

you know the value of (S=O)SO2 so you can rearrange
1
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Current uni students - are you thinking of dropping out of university?

Yes, I'm seriously considering dropping out (155)
14.53%
I'm not sure (46)
4.31%
No, I'm going to stick it out for now (317)
29.71%
I have already dropped out (30)
2.81%
I'm not a current university student (519)
48.64%

Watched Threads

View All