Chemistry Help /
I am struggling with this question, and i'm sure it's because I just missed a step. Can anyone identify what step that is?
http://oi60.tinypic.com/219cv29.jpg
I started with the specific heat capacity of water, then applied the conditions in the problem. But my question is how do we get mols of methanol in there?
*If you know, can you type the answer? I have it, but i'm gonna post a link afterwards requesting you to show your work. :o*
June 15, 2014
4 Comments • Newest first
*Applauds* Someone helpful on Basil for once. Bravo!
@Symphs: You're welcome.
I'm a chem major in college, so if you need any chem help you can just PM me or something and I could totally help if you want.
[quote=NonSonoFronz]q = mass * specific heat * change in temperature
amount of energy needed (joules) = 250 * 4.184*15 = 15690 j
So that answer is how many joules you need to raise that amount of water by 15 degrees.
Now, you need to take a look at that answer in relation the combustion rxn you were given.
So that rxn pretty much says when you burn 2 moles of methanol, an energy of of 1275.8 kj is released. (which can be released and used to heat up that water)
Now think about it this way. You need to moles of methanol to give off 1275.8 kj of heat. How much are you going to need to only give off 15690 j of heat?
WAYYYY less. Now set it up like such:
2 moles of ethanol/1275800 j * 15690 j (so the joules cancel and you are left with moles of methanol) which equals ~0.0246 moles.[/quote]
Welp. There it is. The step I missed. :o
Thank you very much :o
q = mass * specific heat * change in temperature
amount of energy needed (joules) = 250 * 4.184*15 = 15690 j
So that answer is how many joules you need to raise that amount of water by 15 degrees.
Now, you need to take a look at that answer in relation the combustion rxn you were given.
So that rxn pretty much says when you burn 2 moles of methanol, an energy of of 1275.8 kj is released. (which can be released and used to heat up that water)
Now think about it this way. You need to moles of methanol to give off 1275.8 kj of heat. How much are you going to need to only give off 15690 j of heat?
WAYYYY less. Now set it up like such:
2 moles of ethanol/1275800 j * 15690 j (so the joules cancel and you are left with moles of methanol) which equals ~0.0246 moles.