Energetics Flashcards
Define enthalpy change
The amount of heat energy taken or given out during any change in a system provided that the pressure is constant
What are the standard conditions?
100 KPa
298 k
Define standard enthalpy of formation
The Enthalpy change when 1 mole of the compound is formed from its elements under standard conditions with all the reactants and products being in their standard state
Define standard enthalpy of combustion
The Enthalpy change that occurs when 1 mole of a substance is completely burnt in oxygen in their standard conditions, and standard state
What is the equation q=mct used to calculate?
Calculates enthalpy change of a reaction
State the individual units for the equation q= mct
Q- heat change (j)
M- mass of the substance (g)
C- specific heat capacity
T- temperature (k)
Define Hess’s law
The total enthalpy change for a reaction is independent of the route by which the chemical change takes place
What is the formula for Hess’s law?
Define mean bond enthalpy
The enthalpy needed to break the covalent bond into gaseous atoms, averaged over different molecules
How do you calculate mean bond enthalpy?
What is meant by the term endothermic?
Energy is transferred from the surroundings to the system.
Breaking bonds
What is meant by the term exothermic?
Energy is transferred from the system to the surroundings.
Making bonds
