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OpenStudy (photon336):

Another question

OpenStudy (photon336):

Question is attached

OpenStudy (photon336):

@sweetburger @Rushwr

OpenStudy (rushwr):

is it C ?

OpenStudy (photon336):

\[2CH _{4} + 3O _{2} --> 2CO + 4H _{2}O\]

OpenStudy (photon336):

Like i though that for this reaction we have entropy goes up because we have on the reactant side 2+3 moles = 5 moles and on the product side we have 2+4 = 6 moles. So we have more moles on the product side so i thought more moles = more disorder.

OpenStudy (photon336):

\[\Delta G = \Delta H - T \Delta S\]

OpenStudy (photon336):

wait... entropy >0 and if it's spontaneous G<0 so h <0

OpenStudy (rushwr):

aaaah yes

OpenStudy (rushwr):

okai since the product side had more moles than the reactants we took \[\Delta S\] as pistive right? Okai so anyhow the T\[\Delta S\] we consider the whole part as negative. But to find the enthalpy change if its +ve or -ve we need to know if the reaction is spontaneous or not right? But they haven't given that here.

OpenStudy (photon336):

@Rushwr I agree, I had trouble with that, actually I just assumed that the reaction was spontaneous. b/c then I knew okay delta S was positive so then I thought that delta H had to be negative the book doesnt really give an explanation as to how you can figure out that it's exothermic, like it just says oh " this type of reaction is exothermic"

OpenStudy (rushwr):

yeah so this reaction is exothermic

OpenStudy (rushwr):

bond formation is always exothermic while bond dissociation is always endothermic. hence this reaction is exothermic. In exothermic reactions delta H is positive. Cuz it produces heat while in endothermic reactions delta H is negative cuz they absorb heat ! So that is why I choose that one

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