Chapter 4-Energetics Flashcards
What is enthalpy measured in
kJ /mol
What happens to the energy in a system in an endothermic reaction?
Increases
What happens to the energy in a system in an exothermic reaction?
It decreases
What is enthalpy change
The difference in potential energy between reactants and products.
In an exothermic reaction, what is the enthalpy change
negative
In an endothermic reaction, what is the enthalpy change
positive
Is breaking bonds endo- or exothermic
endothermic
Is making bonds endo or exothermic
exothermic
How do you calculate the enthalpy change of a reaction
sum (bonds broken) - sum (bonds made)
What is the standard enthalpy change of a reaction?
Enthalpy change when a reaction occurs in the molar quantities shown in the balanced equation under standard conditions
What is the standard energy change of a formulation?
Enthalpy change when 1 mole of a compound is formed from it constituent elements in their standard states under standard conditions.
What is the standard enthalpy change of combustion?
Enthalpy change when 1 mole of substance is completely burned in oxygen under standard conditions.
What are the standard conditions for measuring enthalpy change?
298 K (25C)
pressure of 1 bar (100 kPa, 1 atm)
If involves solutions, concentration of 1 mol/dm3
What is temperature a measure of?
Average kinetic energy of particles within a substance, independent of the number of particles
What is heat a measure of?
The total energy of all particles in a substance, dependant on the number of particles.
