9.1 Enthalpy Changes Flashcards
What is enthalpy?
heat energy
stored in a chemical system
In an exothermic reaction, is energy overall released or absorbed by the reacting molecules?
released
In an endothermic reaction, is energy overall released or absorbed by the reacting molecules?
absorbed
In an exothermic reaction, how does the temperature of the surroundings change?
increases
(reactant molecules overall release energy to molecules in surroundings)
In an endothermic reaction, how does the temperature of the surroundings change?
decreases
(reactant molecules overall absorb energy from molecules in surroundings)
In an exothermic reaction, the enthalpy of the reactants is _____ than the products.
greater
(since energy is overall released by the reactant molecules)
In an endothermic reaction, the enthalpy of the reactants is ____ than the enthalpy of the products.
lower
(since reactant molecules overall absorb energy to form products)
Is this reaction exothermic or endothermic?
exothermic
(as seen from diagram, enthalpy of products is lower than reactants. therefore overall, energy is released.)
Is this reaction exothermic or endothermic?
endothermic
(as seen from diagram, enthalpy of products is greater than reactants. so overall, energy is absorbed.)
Draw an enthalpy profile diagram for a general exothermic reaction, labelling the activation energy & overall energy change.
In terms of the relative energies when making/breaking bonds, what makes a reaction exothermic?
the energy required to break bonds
is less than
the energy released when bonds are formed.
In terms of the relative energies when making/breaking bonds, what makes a reaction endothermic?
the energy required to break bonds
is greater than
the energy released when bonds are formed
Is forming bonds exothermic or endothermic?
exothermic
Is breaking bonds exothermic or endothermic?
endothermic
What is the formula for calculating enthalpy change?
ΔH = H(products) - H(reactants)
