Energetics Flashcards
What is the definition of enthalpy change
The heat energy change measured under conditions of constant pressure
What symbol and letter denote enthalpy change
∆H
What are standard conditions
298K and 100kPa
How do you convert from Celsius to Kelvin
+ 273
What is on the Y axis of an exo/endo reaction profile
Enthalpy
What is on the X axis of an exo/endo reaction profile
Progress of reaction
Draw an exothermic reaction profile
Draw an endothermic reaction profile
What is the value of ∆H in an exothermic reaction
∆H is negative
What is the value of ∆H in an endothermic reaction
∆H is positive
What happens to the temperature of a solution in an exothermic reaction
Temperature of solution increases
What happens to the temperature of a solution in an endothermic reaction
Temperature of solution decreases
Describe the transfer of heat in an exothermic reaction
Heat transferred from system to surroundings
Describe the transfer of heat in an endothermic reaction
Heat transferred from surroundings to system
Is bond breaking exo or endo?
Bond breaking is endothermic
Is bond formation exo or endo?
Bond formation is exothermic
What is Hess’s law
The enthalpy change at constant pressure is independent of the route taken
What is enthalpy change of formation
When 1mol of a substance is formed from its elements with all reactants and products & in their standard states, under standard conditions
What is standard enthalpy of combustion
Enthalpy change when 1mol of a substance is burned completely in oxygen, with all reactants and products & in their standard states, under standard conditions
What is mean bond enthalpy
Enthalpy required to break a covalent bond averaged over a range of different molecules
Which factor must stay the same in a formation reaction
We cannot change the moles of the product, it must always be 1
Which factor must stay the same in a combustion reaction
We cannot change the moles of the reactant undergoing combustion, it must always be 1
What is the equation for heat energy
q = mc∆T
What is the equation for enthalpy change
∆H = - q/n (q is energy, n is moles)
