Homework Help: chemistry

Posted by jenivy on Monday, February 25, 2008 at 1:55pm.

When 0.911 g of CaO is added to 200.0 mL of 0.500 M HCl(aq), a temperature increase of 374C is observed.
Assume the solution's final volume is 200.0 mL, the density is 1.00 g/mL, and the heat capacity is 4.184 J/gC.
(Note: Pay attention to significant figures. Do not round until the final answer.)
Hrxn, for the reaction of

CaO(s) + 2H+(aq)--> Ca2+(aq) + H2O(l)

chemistry - DrBob222, Monday, February 25, 2008 at 4:55pm
Variations of this problem have shown up at least a dozen times in the last three or four days. I don't know how the temperature of a water solution can increase by 374 degrees C. I suppose it might be technically feasible if we started at absolute zero (-273 degrees C) and moved to 101 degrees C but I think it's highly unlikely to happen. Even then we have steam at 101 and that's still a problem, at least I think it is. Perhaps I'm on the wrong track here. I'll be glad to listen.
My theory is that someone looked up delta H for the reaction, stuck in a number for the mass of CaO, (or Ca for some of the questions I've seen) and mass of water, and worked backwards to get a delta T value. Then that someone didn't think about the unrealistic values for delta T. But that's just my theory.
chemistry - Anonymous, Monday, February 25, 2008 at 6:41pm
the temp sould be 37.4 C ...sorry bout that
chemistry - DrBob222, Monday, February 25, 2008 at 8:57pm
Well, that shoots my theory all to H-ll. It's as simple as a typo. Thanks for letting me know.

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