Top Posters
Since Sunday
5
a
5
k
5
c
5
B
5
l
5
C
4
s
4
a
4
t
4
i
4
r
4
Home Q & A Board Science-Related Homework Help Chemistry (Moderator: Laser_3)
New Topic  
Zomgnades Zomgnades
wrote...
Go to Answer
Posts: 6
Rep: 0 0
11 years ago
Standard enthalpy of formation values in kJ mol-1:
CO2 (g) = -394
H2O(l)= -286
C2H4(g)= +52
Read 471 times
2 Replies
Replies
Answer accepted by topic starter
mig9399mig9399
wrote...
#1
Posts: 49
Rep: 0 0
11 years ago
Sign in or Sign up in seconds to unlock everything for free
1

Related Topics

wrote...
#2
11 years ago
well best way to do it is drawing out hess' cycle.

you want combustion of ethene so put that at the top:
and balance it:
C2H4+ 3O2 --------------------------------> 2CO2+2H2O

then you work out what kind of cycle it is:

i think its the element one so you put elements at the bottom

C (s)+ H2 (g) + O2 (g)

balance it:

2C (s)+ 4H (g) + 6O (g)
then you like put arrows ffrom this up to C2H4+ 3O2

and another arrow up to 2CO2+2H2O

Write in the enthalphys

so arrow going up to C2H4+ 3O2  is the formation of C2H4
which is +52KJ mol-1

arrow going up to 2CO2+2H2O will be -394KJmol-1 x 2 + -286KJmol-1 x 2=

-788+-572
= -1360

Standard enthalphy change= 52--1360=
1412KJmol-1

i think this is how you work it out =]]
New Topic      
Quick Reply
Explore
Post your homework questions and get free online help from our incredible volunteers
  1414 People Browsing
Start New Topic Take the Tour CoursesNew Study Tools Topics Trending Browse by Textbook
Related Images
  
 368
  
 189
  
 127
Your Opinion
What percentage of nature vs. nurture dictates human intelligence?
Votes: 431
Previous poll results: How often do you eat-out per week?