Chapter 9 - Enthalpy Flashcards
what is enthalpy H?
a measure of the heat energy in a chemical system
What is enthalpy change 🔺H?
the difference in enthalpies of the products and reactants
how can 🔺H be calculated?
H(products) - H(reactants)
do exothermic products have a negative or positive 🔺H?
negative
do endothermic products have a negative or positive 🔺H?
positive
what is the activation energy Ea?
the minimum energy required for a reaction to take place
what is standard physical value and it’s units?
refers to a reaction under standard conditions, units are KJ mol ^-1
what is the enthalpy change of reactions 🔺rH🔴?
the enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions
what is the enthalpy change of formation 🔺fH🔴?
the enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions
what is the enthalpy change of combustion 🔺cH🔴?
the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions
what is the enthalpy change of neutralisation 🔺neut H🔴?
the energy change that accompanies the reaction of an acid by a base to form one mole of H2O under standard conditions
what is the equation for heat energy q?
q= m c 🔺T
what is average bond enthalpy?
the energy required to break one mole of a specified type of a bond in a gaseous molecule
why can the actual bond enthalpy vary?
different chemical environnements
how can you calculate the enthalpy change of reaction 🔺rH?
🔺rH= { (bond enthalpies in reactants) - { (bond enthalpies in products)
