energy balance with chemical reaction Flashcards
(20 cards)
types of heat reactions
exothermic and endothermic reaction
a reaction that releases heat to the surroundings
exothermic reaction
a reaction where temperature increases around a system
exothermic reaction
a reaction where the system loses enthalpy (∆H<0; negative)
exothermic reaction
a reaction that absorbs heat from the surroundings
endothermic reaction
a reaction where the temperature drops around the system
endothermic reaction
a reaction where the system gains enthalpy (∆H>0; positive)
endothermic reaction
enthalpy changes when 1 mole of a compound is formed from its elements in their standard conditions
heat (enthalpy) of formation
state of enthalpy change
25°C and 1 atm
when does the enthalpy changes
when a chemical reaction occurs under standard conditions
represents the overall heat absorbed or released during a reaction
enthalpy of reaction
tells how much heat energy is involved when substances react to form new ones
heat (enthalpy) of reaction
standard state of a substance in its most stable form
at a pressure of 1 bar (or 1 atm) and a specified temperature, usually 25°C (298.15K)
it does not mean “normal” conditions (like room air) – it’s a chosen reference point
standard state
used when reporting values like enthalpy of formation or Gibbs free energy
standard state
the heat of any reaction for a specific reaction is equal to the sum of the heats of reaction for any set of reactions, which in sum are equivalent to the overall reaction
Hess’s Law of Constant Heat Summation
we can use the extent of reaction to obtain this only for steady state flow
heat of reaction
the enthalpies of reaction and formation can be incorporated under the enthalpy term of the general energy balance
energy balance with chemical reaction
enthalpy in the balance is a combination of the individual enthalpy terms
energy balance with chemical reaction
in simple terms it shows how much energy does it take to make 1 mole of a substance from scratch using raw ingredients from nature
heat (enthalpy) of formation
