energetics Flashcards
what is enthalpy change?
change in heat energy of a substance under constant pressure
what does an exothermic reaction do?
release energy into the surroundings
what does an endothermic reaction do?
take in energy from the surroundings
what does a +ve deltaH value mean?
the reaction is endothermic
what does a -ve deltaH value mean?
the reaction is exothermic
at what conditions does a standard enthalpy change occur?
100KPa
298K
what is the standard enthalpy of combustion?
the enthalpy change under standard conditions when 1 mole of a substance is burned completely in excess oxygen, with all reactants and products in their standard state
what is the standard enthalpy of formation?
the enthalpy change under standard conditions when 1 mole of a compound is formed from its elements, with all reactants and products in their standard state
what is calorimetry used for?
measuring the heat energy change in a reaction
what is the equation to calculate the energy required (q)?
q = m x c x deltaT
what are errors in calorimetry mainly due to?
heat loss to the surroundings
how can we prevent heat loss in a calorimetry experiment?
use insulating materials
what does hess’ law state?
the enthalpy change of a reaction is independent of the route taken
what is the equation for deltaH of formation
deltaH = sum of products + sum of reactants
what is the equation for deltaH of combustion?
deltaH = sum of reactants - sum of products
