ENERGETICS Flashcards
what is enthalpy
heat energy change in a reaction uder standard conditions
what are the standard conditions ?
298K
100kPa
what are the two types of reactions?
endothermic
exotheermic
what is an endothermic reaction?
when energy is absorbed from the surroundings
where is the position iif the products in an endothermic reaction
at thee top
what is an exothermic reaction?
when energy is released to the surroundings
what happens to the suroundings during an exothermic reaction?
it gets warmer
where is the position of the products in an exothermic reaction
its lower
what type of reaction is a bond breaking one?
endotheermic
why is it an endothermic reaction when bonds are madde
heat is absorbedd
what type of a reaction is bond making
exothermic
why is it an exothermic reaction when bonds are broken
energy is releeased
what is an example of an exothermic reaction?
combustion
what is standard enthalpy of formation
enthaphy change required to forrm 1 mole of a compound from its constituent elements under standard conditions
298K
100kPA
what is standard enthalpy of combustion
the enthalphy change required to completely burn 1 mole of a compound in excess oxygen under standard conditions
298K
100kPA
what does calorimetry allow us to see
enthalpy change of a reaction
how can wecalculate thee enthapy change
kJ/mol
what is burnt in calorimtry
the fuel
what are tthe steps of calorimtry
meausre the inital mass of fuel
find inital temperature of water
light up fuel
energy from fuel will increase the temp of water
what is the purpose of the fuel
so that the energy from the fuel will increase the temp of water
sometimes the enthalpy change of or reaction is less than the actual one
why is that?
heat is lost to surroundings
-heat is absorbed by container
-incomplete combustion
-evaporation (volatile fuel)
what is Hess’s LAw
enthalphy change is the same as whatever route it takes
where do the arrows go for enthalpy of formation
down then up ——
up up
where do the arrows for enthalpy of combustion
down then up ——
down down
what is bond enthalpy
the avergae energy needed to break covalent bonds over a range of compounds
what is the difference between Hesses Law and Bond enthalpies
hesses law is the actual values of bod enthalpy in that reaction
bond enthalpy- mean values across compounds containing bond
what is the state of the molecules in bond enthalpy
gaseous state
