# as level chemistry help 😢😢😢Watch

Thread starter 4 weeks ago
#1
(b) Some bond energies are given.
bond bond energy / kJmol–1
S=O (in SO2) 534
O=O 496
Use the data, and the enthalpy change for the conversion of sulfur dioxide into sulfur trioxide,
to calculate a value for the S=O bond energy in SO3.
S=O bond energy in SO3 = .............................. kJmol–1 
0
4 weeks ago
#2
Start by writing out the balanced chemical equation, then work out how much energy is required to break all the bonds, then how much energy is released when all the new bonds are formed 0
Thread starter 4 weeks ago
#3
the equation is balanced
0
Thread starter 4 weeks ago
#4
the ans that i have calculated is different form the original ans. 0
4 weeks ago
#5
(Original post by shah kaivan)
the ans that i have calculated is different form the original ans. You really should post the whole question Did they give you the balanced equation? What value have they given the enthalpy change of formation of SO3.

What answer did you get?
Last edited by EierVonSatan; 4 weeks ago
0
Thread starter 4 weeks ago
#6
ok
s=o 1068 + o=o 496 == s=o 1602
1068+496-1602
0
Thread starter 4 weeks ago
#7
so my ans is -38
0
4 weeks ago
#8
(Original post by shah kaivan)
so my ans is -38
Bond enthalpies are always positive so you shouldn't need the answer to tell you something has gone wrong.

Step 1: Balanced chemical equation

SO2 + 0.5O2 → SO3 where ΔHf = -396 kJ mol-1 (value taken from a data book, the value you have might be different)

Step 2: Work out energy needed to break bonds

SO2 contains 2 x (S=O) bond, O2 has 1 (O=O) bond but have only half a mole of this!

Bonds broken = 2 x 534 + 0.5 x 496 = 1316 kJ mol-1

Step 3: Work out energy needed to form the new bonds

ΔHf = bonds broken - bonds formed

-396 kJ mol-1= 1316 kJ mol-1 - 3(S=O)

Can you finish it off?

Seems not Last edited by EierVonSatan; 4 weeks ago
0
Thread starter 4 weeks ago
#9
this is in the mark scheme
−196 + 6S=O = (4 × 534) + 496 1

S=O = 2828 / 6 = 471(.3)
0
Thread starter 4 weeks ago
#10
how did he multiply it by 6
0
4 weeks ago
#11
(Original post by shah kaivan)
how did he multiply it by 6
It looks like they've used 2SO2 + O2 → 2SO3 as their balanced equation, which is fine but to do that you also need to use 2ΔHf
0
Thread starter 4 weeks ago
#12
do you have mark scheme of save my exam website
0
Thread starter 4 weeks ago
#13
in this website topical past papers are given but ms is not free
0
Thread starter 4 weeks ago
#14
2.00 moles of nitrogen and 3.00 moles of hydrogen were put in a vessel and left to reach
equilibrium.
At equilibrium, the pressure was 2.00 × 107Pa and the mixture contained 1.60 moles of
ammonia.
Calculate Kp. Include the units.
0
Thread starter 4 weeks ago
#15
my ans
n2 h2 2nh3
2 3 0
Y X 1.60

how to find x and y
0
4 weeks ago
#16
(Original post by shah kaivan)
(b) Some bond energies are given.
bond bond energy / kJmol–1
S=O (in SO2) 534
O=O 496
Use the data, and the enthalpy change for the conversion of sulfur dioxide into sulfur trioxide,
to calculate a value for the S=O bond energy in SO3.
S=O bond energy in SO3 = .............................. kJmol–1 
Is this your homework question from school?

Sadly your teacher would be disappointed with you asking strangers to solve the question for you
0
X

new posts Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

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

### University open days

• Regent's University London
Thu, 19 Sep '19
• Durham University
Pre-Application Open Days Undergraduate
Fri, 20 Sep '19
• Loughborough University
Fri, 20 Sep '19

### Poll

Join the discussion

Rock (164)
24.59%
Pop (164)
24.59%
Jazz (26)
3.9%
Classical (40)
6%
Hip-Hop (121)
18.14%
Electronic (43)
6.45%
Indie (109)
16.34%