Enthalpy Flashcards
what is the enthalpy change
the heat change in a reaction at constant pressure
what are the standard conditons for enthalpy change
100kPA pressure
298K temperature
what does the Ø indicate
substance was in standard state under standard conditions
if a reaction absorbs heat energy from the surrounds what type of reaction is it
endothermic > heat ENters the reaction
if heat energy exits a reaction into the surroundings what type of reaction is it
exothermic
is breaking of bonds an exothermic or endothermic reaction
breaking of bonds is endothermic because energy is absorbed
is the formation of bonds and exothermic or endothermic
exothermic because energy is released when bonds are formed
what is mean bond enthalpy
the total bond enthalpy / number of bonds
(of same type)
formula for enthalpy change
total energy to break bonds - total energy released forming bonds
what is calorimetry used for
to work out enthalpy change of combustion
what is the difference between enthalpy change and energy transferrred
enthalpy change is kj per mole
energy transferrred is kj
what equation is used to work out energy from acalorimetry experiment
q = mc(delta)T
outline step by step how to work out enthalpy change with the calorimetry experiment / q=mc(delta)T
- work out energy transferred with q=mc(delta)T
- work out moles of the substance > mass/MR
- work out enthalpy > q / moles
how do you work out energy from calorimetry experiment of SOLUTIONS
- use q=mc(delta)T > add up masses of both substances
- work out moles > conc X vol (convert to dm3)
- work out enthalpy > q/moles
how do you determine if the energy transferred value from calorimetry should be a negative or not
- exothermic reaction > negative
- endothermic reaction > positive
