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)

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  1. Someone will be glad to check your answers if you give your best shot and tell us why you answered as you did.

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  2. Umm this question is on our Quiz 5 ... anyways I don't 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 don't know about the work part

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  3. 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

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  4. nvm, i did some reworking

    heres what my final answer


    can someone confirm please?

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  5. yes.. i got the same answer :)

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