Which of the following defines a reaction that is temperature- dependent?

[mouthcracker]

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- Which of the following defines a reaction that is temperature- dependent?
o +delta H, +delta S
o +delta H, -delta S
o –delta H, +delta S
o –delta H, -delta S

 

[Streetwolf]

Both + or both -. The +/- and -/+ are NOT temp dependent.

Formula is G = H - TS (didn't include the deltas). So with +/- you have G = +H - T(-S) = +H + TS which is always + because T is absolute temperature (always +).

With -/+ you have G = -H - T(+S) = -H - TS which is always - because T will be positive.

With +/+ you have G = +H - T(+S) = +H - TS. Now if H > TS you'll have H - TS > 0 and if H < TS you'll have H - TS < 0. Since H and S are fixed, the reaction depends on T. So if T < H/S then G > 0 and if T > H/S then G < 0 (try for yourself!).

With -/- you have G = -H - T(-S) = -H + TS. The signs are all flipped for this one. With a large enough T the value of G will be positive. With a small enough value of T the value of G will be negative.