This isn't endothermic, is it?

[blackmi4]

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20 grams of NaCl is poured into a coffee cup calorimeter containing 250ml of water. If the temperature inside the calorimeter drops 1degC by the time the NaCl is totally dissolved, what is the heat of solution for NaCl and water? (specific heat of water is 4.18J/g degC.

Answer given:

3 kJ/mol

First figure out the heat evolved by using q=mcdT.q=250g*4.18J/gdegC*1degC=1050J.
Next divide by moles of NaCl (20g is about 1/3 a mole). This gives you 3150 joules, which is equal to 3kJ. Since the temperature went down, the reaction is endothermic with positive enthalpy. Notice all the rounding.

Is it endothermic? Wouldn't temperature increase if it was endothermic? The system became cooler -- lost heat -- isn't it exothermic?

Thanks!

 

[FeinMS]

No, endothermic -> absorbs heat from the surrounding -> the surround temp decreases

 

[blackmi4]

No, endothermic -> absorbs heat from the surrounding -> the surround temp decreases

Ok. So when they say the temperature inside the calorimeter decreased they were referring to the surroundings and not the system. Ok.

Thanks!