energetics Flashcards
what is enthalpy change
it is the heat energy change measured under conditions of constant pressure
reactions can either be what ? (energetics)
exothermic or endothermic
what are standard conditions
100kpa
298K
standard states of the substance
what is standard enthalpy of combustion
enthalpy change when one mole of a substance is completely burned in oxygen in standard states and conditions
what is standard enthalpy of formation
enthalpy change when one mole of a substance is formed from constituent elements under standard conditions
what to endothermic reactions do to temp of surroundings
decrease temp of surroundings ∆+
what to endothermic reactions do to temp of surroundings
increase temp of surroundings ∆-
heat change reaction (q=)
q=mc∆T
what does the m stand for in q=mc∆T
mass of substance
what does the c stand for in q=mc∆T
specific heat capacity
what does the ∆T stand for in q=mc∆T
change in temperature
what are the issues with calorimetry
- incomplete reaction
- incomplete combustion
- heat loss to surroundings
what information do bond enthalpies provide
they provide info on how much energy is required to break bond
are bond enthalpies specific to each molecule
yes
∆H =
sum of bonds broken - sum of bonds formed
show an example of hess law using A -> B
show the example way of writing enthalpy change of combustion
show the example way of writing enthalpy change of formation
