MCAT chemistry question

[callmesubo]

Hey Guys, I have a question regarding endothermic reaction and exothermic reaction. A reaction between NaOH and HCl in coffee cup calorimeter takes place and the temperature of the solution increases. Now would you call this an endothermaic or exothermic. I thought it's endothermic since DeltaH is positive. but according to examkracker heat is released because the temperature of the solution rises. Hope someone can resolve my confusion.

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[RaspberrySlushy]

DeltaH is negative.

 

[swollcat]

Hey Guys, I have a question regarding endothermic reaction and exothermic reaction. A reaction between NaOH and HCl in coffee cup calorimeter takes place and the temperature of the solution increases. Now would you call this an endothermaic or exothermic. I thought it's endothermic since DeltaH is positive. but according to examkracker heat is released because the temperature of the solution rises. Hope someone can resolve my confusion.

Acid-base neutralization rxns release heat and are therefore exothermic

 

[El-Rami]

Acid-base neutralization rxns release heat and are therefore exothermic

Yep. This is the rationale behind why you never add water to [strong] acid. You add acid dropwise to water because the reaction is highly exothermic.

 

[Ryuichi]

the temperature of the solution as the rxn is occurring, without any mention of heat added represents the temperature being output by the reaction. therefore a hot rxn is exothermic. Endothermic rxns require heat input as a reactant.

 

[Cristian]

A reaction that releases heat is exothermic. It has a negative delta-H because the enthalpy of the products is lower than the enthalpy of the reactants.

 

[NextStepTutor_3]

Yeah, it's all in the difference between the system and the surroundings. It's easy to think that because temperature increased, the reaction must have been endothermic, or that heat must have somehow been added. But remember, the interior of the calorimeter (the surroundings) is not the same as the reactants themselves. If calorimeter temperature goes up, that means that the reaction itself released the heat that promoted this change.