1.4 Energetics Flashcards
1
Q
what is enthalpy change?
A
- amount of heat energy taken in or given out during any change in a system provided the pressure is constant
2
Q
what happens in an exothermic energy change?
A
- energy is transferred from the system to the surroundings
3
Q
what happens in an endothermic energy change?
A
- energy is transferred from the surroundings to the system
- products have more energy than the reactants
4
Q
what is the standard enthalpy of formation?
A
- enthalpy change when one mole of a compound is formed from its elements under standard conditions, 298K and 100kPa, all reactants and products being in their standard states
5
Q
what is the enthalpy change of combustion?
A
- enthalpy change when one mole of a compound is completely combusted in oxygen under standard conditions, 298K and 100kPa, all reactants and products being in their standard states
6
Q
what will incomplete combustion lead to?
A
- soot, carbon monoxide and water
- less exothermic than complete combustion
7
Q
state Hess’s Law
A
Hess’s Law states that the total enthalpy change for a reaction is independent of he route taken
8
Q
the enthalpy of combustion determined experimentallly is less exothermic than that calculated using enthalpies of formation,
give one possible reason for this other than heat loss
A
incomplete combustion
