Physical Chemistry Flashcards
1
Q
When the enthalpy change is negative is the reaction exothermic or endothermic?
A
The reaction is exothermic as more energy is released in bond making than is absorbed in bond breaking
2
Q
When the enthalpy change is positive is the reaction endothermic or exothermic?
A
The reaction is endothermic as more energy is absorbed in bond breaking than is released in bond making
3
Q
How do you calculate the enthalpy change from average bond enthalpies?
A
(Sum of bond enthalpies of the reactants) - (Sum of bond enthalpies of products)
4
Q
In a Hess cycle of combustion do the arrows point up or down?
A
They point downwards
5
Q
In a Hess cycle of formation do the arrows point up or down?
A
They point upwards
