Enthalpy Change Flashcards
What is an exothermic reaction?
Heat flows from the system to to the surrounds.
What is an endothermic reaction?
Heat floes from the surroundings to the system
Define enthalpy change
The heat change at a constant pressure
What are the units for Enthalpy change
KJ mol-1
What is the enthalpy change for exothermic reactions?
Negative values
What is the enthalpy change for endothermic reactions?
Positive values
How does mass affect the temperature change?
The higher a substance’s mass, the smaller its temperature increases
Define specific heat capacity
The amount of energy required to raise the tempe of one grand of that substance by 1 kelvin.
What are standard conditions?
100,000 Pa
298K
Define standard enthalpy of formation
Enthalpy change when 1 mole if a substance forms from its constituent elements in their standard states under standard conditions.
What is the enthalpy change for any element?
0 KJ mol-1
Define the enthalpy of combustion
The enthalpy change when 1 mile if a substance is burned completely in oxygen under standard conditions.
What is hess’ law?
The enthalpy change of a reaction is independent of the route taken
