Hedwigeeeee
Badges: 18
Rep:
?
#1
Report Thread starter 9 months ago
#1
which process measures the mean bond enthalpy for the C-H bond in methane?
A. CH4----->CH3+H2
delta H =A,mean bond enthalpy=A
B. CH4------>C +4H
delta H=B, mean bond enthalpy=B/4
and the correct answer is b, why, and what is the difference between the mean bond enthalpy represented by A and B?
0
reply
Kian Stevens
Badges: 16
Rep:
?
#2
Report 9 months ago
#2
B represents the enthalpy change of atomisation of methane, in which each C-H bond is broken and B kJ mol-1 of energy is required to do it

However, this is the total amount of energy required to break all four C-H bonds, and so to find the mean bond enthalpy (i.e. the average bond enthalpy of one C-H bond) you have to divide B by four; you can kind of imagine this as B's units becoming kJ mol-1 bond-1

N.B. As a side note, A doesn't actually represent a correct process, so this is kind of a trick question too
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

Are you travelling in the Uni student travel window (3-9 Dec) to go home for Christmas?

Yes (56)
29.02%
No - I have already returned home (24)
12.44%
No - I plan on travelling outside these dates (44)
22.8%
No - I'm staying at my term time address over Christmas (18)
9.33%
No - I live at home during term anyway (51)
26.42%

Watched Threads

View All
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