10.5 Calorimetry- 10.4 Exothermic and Endothermic processes Flashcards
Calorimeter
A device used to measure the amount of heat absorbed or released during chemical/physical processes
Calorimetry
The accurate & precise measurement of heat change in a chemical/physical process
Enthalpy
‘H,’ it is a property equivalent to heat content (q) in a system at constant pressure.
∆H is the heat change in a substance, while at constant pressure the changes in enthalpy are the same as ∆H. (q = enthalpy = ∆H)
The sign for ∆H is - for an exothermic reaction and positive for an endothermic reaction
The calorimetry equation
q= delta H= m x C x delta T
The heat is equal to delta H, m is the mass of H2O, C is the specific heat capacity of the water, and delta T is the change in temperature of the water (after-before)
Aqueous solutions will be mixed together to measure heat change in the reaction, rather than just physically heating it.
The specific heat of water
4.18 J/ g of H2O °C, or 1 cal/ 1 g of H2O °C
system
The specific part of the universe on which you focus your attention.
A typical system may be the chemicals that undergo a reaction.
surroundings
Includes everything outside of the system.
The surroundings may be a pool of water that surrounds a flask of chemicals
universe
Together the system and surroundings make up a universe.
Its okay to consider only the immediate surroundings with the system a universe.
endothermic process
In thermochemical calculations the direction of heat flow is based on what system is focused.
A system that absorbs heat from its surroundings is endothermic.
exothermic process
A system that loses heat to its surroundings is exothermic.
Heat change is measured on the heat of the system, endothermic reactions are positive because the heat in the system increases, while exothermic processes are negative because heat is lost.
