Homework Help: Chemistry

Posted by victor on Sunday, November 22, 2009 at 7:14pm.

Label each of the following reactions as exothermic or endothermic ("exo" or "endo"), and according to whether work is done on or by the system, or no work is done at all ("on", "by" or "none")? Note that no "endo-on" cases appear here, as these are always thermodynamically unfavourable. There is no need to do any calculation, use chemical arguments to predict the sign of the enthalpy change.
Matching pairs
N2(l) --> N2(g)

Cl2(aq) + 2 KBr(aq) --> 2 KCl(aq) + Br2(aq)

Zn(s) + 2HCl(aq) --> ZnCl2(aq) + H2(g)

NH3(g) + HCl(g) --> NH4Cl(s)

S(s) + 3/2 O2(g) --> SO3(g)

Chemistry - Jeff Landry, Sunday, November 22, 2009 at 7:46pm
Do it yourself.
Chemistry - DrBob222, Sunday, November 22, 2009 at 7:46pm
Someone will be glad to check your answers if you give your best shot and tell us why you answered as you did.
Chemistry - Mcmaster Student :D, Monday, November 23, 2009 at 12:18pm
Umm this question is on our Quiz 5 ... anyways I dont understand the concept really i understand that when you are breaking bonds you need energy and when you making bonds you release energy ... and for work I think you need to look at the volume gas yet I am not sure about that part :(
for first question : exothermic you need energy to break bonds and form gasous forms and so on ... yet i dont know about the work part
Chemistry - zack, Tuesday, November 24, 2009 at 6:09pm
Okay, so basically i think i got all the endo and exo figured out because of either state change (heat released or used) but how do i figure out the "on", "by" or 'none' part?

1) exo
2)exo
3)endo
4)exo
5)exo
Chemistry - zack, Tuesday, November 24, 2009 at 6:40pm
nvm, i did some reworking

heres what my final answer

endo-by
exo-none
exo-by
exo-on
exo-on

can someone confirm please?
Chemistry - CHEM MAC, Tuesday, November 24, 2009 at 9:09pm
yes.. i got the same answer :)

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