Energetics Flashcards
Enthalpy Change
Enthalpy change is the amount of heat energy lost or gained during any change in a system provided the pressure is constant.
Define exothermic?
Energy is transferred from the system to the surroundings and the products have less energy than the reactants.
Define endothermic?
Energy is transferred from the surroundings to the system and the products have more energy than the reactants.
What are standard conditions?
298 K, 1atm (100kpa), 1moldm⁻³
What is the standard enthalpy of combustion?
The enthalpy change when one mole of a substance is completely combusted with oxygen under standard conditions.
When performing a calorimetry experiment where are the sources of error?
Heat loss to surroundings
Approximation of SHC
Heat absorbed by apparatus
Reaction incomplete
Density is taken to be the same as water
What is the mean bond enthalpy?
The enthalpy change to break 1 mole of bonds averaged over many molecules
What is Hess’s law?
The enthalpy change in a reaction is independent of the route taken
What to remember when writing equations for the standard enthalpy of formation of a compound?
The product or reactant must be a single mole
There must be state symbols
State the meaning of enthalpy change?
Heat change at constant pressure.
