CHEM 191 Lecture 10 Flashcards
what is energy
the capacity to do work of transfer heat
what are the two types of energy (for CHEM 191)
kinetic energy - energy of motion
potential energy - energy of position
what is work
energy used to change the position of an object
what is heat
energy used to change the temperature of an object
Eproducts - Ereactants =
∆rE - can also be final minus initial
if the change in heat is negative is the reaction exothermic or endothermic
exothermic - energy is lost by the system and gained by the surroundings
how do you find change in heat
final minus initial
if the change heat is positive is the reaction exothermic or endothermic
endothermic - energy is gained by the system and lost from the surroundings
when there is no change in atmospheric pressure what is change in heat equal to
enthalpy
why are state symbols important in enthalpy equations
because there is a change in energy when you change the state of something
what does hess’s law state
if a reaction is conducted in a series of steps the change in enthalpy for the overall reaction will equal the sum of the enthalpy changes for the individual steps
when doing hess’s law calculations if you reverse an equation what must you do to the enthalpy
change the sign - negative to positive or positive to negative
when doing hess’s law calculations if you multiply the equation what must you do to the enthalpy
multiply it by the same amount
what is a formation reaction
the formation of 1 mole of a compound from its constituent elements in their standard states (the most stable form of the element under normal conditions)
how do we calculate the change in enthalpy for the reaction
the total enthalpy of formation for the products minus the total enthalpy of formation of the products - all under standard conditions
