High quality coal (anthracite) is almost pure carbon. The combustion of carbon to carbon dioxide releases 393kJ per mol of carbon burnt. If 1kg of anthracite is burnt:

Question

a) How much heat is released?
b) How much ice (in kg) at 273K could be melted to give water at 273K?
c) How much ice at 273K could be melted to give water at 100degrees celcius?
d) How much ice at 273K could be melted to give steam at 373K?

I found a) to be 32723kJ.
But I don't know how to do the rest.
I know it has something to do with enthalpy of fusion.

Please help.
Thanks

Answer 1

b.
q = mass x heat fusion
q about 32,723,000 J
heat fusion about 334 J/g
Solve for mass ice.
You should confirm the 334 value.

c.
q = [mass ice x heat fusion ice] + [mass water x specific heat water x delta T]
Let mass ice = mass water = x and solve for x.

d. Same procedure but include heat vaporization at 100.
Note the correct spelling of celsius.

Answer 2

Your answer to (a) looks correct.
For (b), divided the heat release by the heat of fusion of water, 333 Kj per kg.
For (c), divide the heat realse by (333 +418 kJ) = 551 kJ/kg
For (c) add the heat of vaporization to the amount of heat required per kg, and divde that into the heat release.

Answer 3

Your answer to (a) looks correct.
For (b), divided the heat release by the heat of fusion of water, 333 Kj per kg.
For (c), divide the heat realse by (333 +418 kJ) = 551 kJ/kg
Note:I believe drwls make a typo here. I think he meant to type 751 and not 551. :-)
For (c) add the heat of vaporization to the amount of heat required per kg, and divde that into the heat release.

Answer 4

Thank you,

I still can't seem to get the last one.
We are given our data in kJ/mol

So would
q = n (heat fusion ice + heat sublimation ice + (heat capacity water x delta T)) ?

We also don't have the heat vaporisation value. Only for sublimation - is it the same? They only give vaporisation values for specific elements, such as Hydrogen, Oxygen etc, but not compounds.