Specific heat capacity  [ENDORSED]

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Specific heat capacity

Postby Eman_Burney_1D » Sat Jan 14, 2017 11:27 pm

On page 20 of our course reader, dealing with water, the amount of heat released is -2.9 kJ. Is the answer negative because
H + OH ---> H2O is an exothermic reaction (because a bond is being formed, thus giving off heat), and the fact that an exothermic reaction means delta H is negative? Or does it have to do with the information about a perfect system (qsys + qsurr=0)? Thanks!

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Re: Specific heat capacity  [ENDORSED]

Postby Brandon_Phan_3J » Sun Jan 15, 2017 12:25 am

I believe the answer is negative because the formation of water by its elements is exothermic, and yes because delta H is negative, it would imply that the reaction is exothermic. Hope this helps!

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Re: Specific heat capacity

Postby Katherine_Zhuo_3B » Sun Jan 15, 2017 8:16 pm

In a reaction, anytime a bond is formed, it is an exothermic reaction. This is because energy is released when the bonds are formed. To express that the reaction is exothermic, the delta H is negative. In a perfect system where qsys =- qsurr, this equation is derived from the 1st Law of Thermodynamics, where the total energy of the universe is constant. Therefore, energy released by the system is absorbed by the surroundings and vice versa. Hence, if heat is given off, the q is positive, and heat absorbed is negative.

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