# Question on enthalpy change

Watch
Announcements
#1
Attachment 607980607982 for q2b I am unsure how it's worked out.

1. How will you be able to deduce that the Mr of coal is just 12 g mol^-1? You are not told the molecular formula for it .

2. The answer suggests that you will work out the heat loss q from the moles of coal * by the enthalpy change of combustion but I don't understand why. Why is q of coal = q of water ?

Thanks
0
4 years ago
#2
The question says assume coal is pure carbon. Carbon is in the periodic table!
0
4 years ago
#3
Use Q = mcΔT for 2b)
0
#4
(Original post by TeachChemistry)
The question says assume coal is pure carbon. Carbon is in the periodic table!
So whenever the question states the the compound is made up of carbon, it is okay to assume that the mr is 12?

Also can you help me with my second question?

Thanks
0
#5
(Original post by TeachChemistry)
Use Q = mcΔT for 2b)
I don't really understand why q of the coal equals to q of the water, I always know it as that you would only include the mass of the water in this equation...
0
4 years ago
#6
(Original post by coconut64)
I don't really understand why q of the coal equals to q of the water, I always know it as that you would only include the mass of the water in this equation...
You assume that all of the heat released by the coal burning is transferred to the water to heat it up.
0
#7
(Original post by TeachChemistry)
You assume that all of the heat released by the coal burning is transferred to the water to heat it up.
Thanks.
0
4 years ago
#8
(Original post by TeachChemistry)
You assume that all of the heat released by the coal burning is transferred to the water to heat it up.

Does anybody know how to work this out? It was from the new Aqa Chem AS paper 2016 Thank You
0
#9
(Original post by PBC Gyal)

Does anybody know how to work this out? It was from the new Aqa Chem AS paper 2016 Thank You
Hey I just worked this out but can't find the paper nor the mark scheme, mind telling me the answer ? Cheers
0
4 years ago
#10
(Original post by coconut64)
Hey I just worked this out but can't find the paper nor the mark scheme, mind telling me the answer ? Cheers
0
4 years ago
#11
(Original post by coconut64)
Hey I just worked this out but can't find the paper nor the mark scheme, mind telling me the answer ? Cheers
Hey and yes I got around 11570KJ it was the AqaChem new spec done in2016
0
4 years ago
#12
(Original post by TeachChemistry)
Use Q = mcΔT for 2b)

Attachment 609428609430Do you know how to work this out? The last image is the graph for the question above please
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.

### Poll

Join the discussion

#### Feeling behind at school/college? What is the best thing your teachers could to help you catch up?

Extra compulsory independent learning activities (eg, homework tasks) (18)
7.5%
Run extra compulsory lessons or workshops (35)
14.58%
Focus on making the normal lesson time with them as high quality as possible (43)
17.92%
Focus on making the normal learning resources as high quality/accessible as possible (34)
14.17%
Provide extra optional activities, lessons and/or workshops (63)
26.25%
Assess students, decide who needs extra support and focus on these students (47)
19.58%