Calorimetry & Enthalpy

1. The problem statement, all variables and given/known data
For the reaction 2H2O(l) -> 2H2(g)+O2(g) delta H = +571.5 kJ

If the reaction is carried out in an insulated chamber what effect would the reaction have on the temperature in the chamber? Why?

The attempt at a solution
I can't seem to get my head around this one. I know the sign on the enthalpy change is from the point of view of the system...but what really qualifies as the system and the surroundings if there is no real boundary between them?
 
Wait...if I look at the equation
delta H=-CdeltaT

In order for delta H to be positive wouldn't temperature change have to be negative?
 

Ygggdrasil

Science Advisor
Insights Author
2,784
1,820
A positive ΔH indicates that the reaction is endothermic; the reaction requires the absorption of heat in order to proceed. So, you are correct. The temperature will decrease because the reaction absorbs heat from its surroundings.
 

The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top