lecture 5 Flashcards
is combustion of hydrogen exo or endo
exo
what does exo mean in terms of enthalpy
decrease in enthalpy
-๐บH
is the haber bosch process exo or endo
exo
is photosynthesis endo or exo
endo - uses light energy
what does endo mean in terms of enthalpy
enthalpy increases
+๐บH
what is the second law or thermodynamics
S, entropy of an isolated system increases in the course of a spontaneous change
๐บs > 0
how does more heat mean higher entropy
more heat = more disorganised motion
= more disorder
= increase in entropy
what is entropy
measure of disorder
what are the 2 change in entropy equations
dS = dq (in a reversible process) ///// T
๐บs = integral { dq(rev) / T
limits = final state - initial state (temp)
what is ๐บS
change in entropy
what is ๐บs at a constant temperature
๐บs = ๐บq/T
what is another way of phasing the 2nd law of thermodynamics
entropy of an isolated system can never decrease
entropy of surroundings or system will increase
๐บs of universe equation
๐บs universe = ๐บs system + ๐บs surroundings
equal to or bigger than 0
what happens to entropy as u go from hot to cold
overall entropy increases
entropy decreases
HOT : ds = - dq/ T
COLD : ds = dq / T
cold to hot will always have a higher entropy as itโs not negative
what is cool about the amounts of heat gained by 2 objects
gain the same amount of heat but opposite
- 20
+ 20
how to do u go from the molar heat capacity to the total heat capacity in a reaction
multiply the molar heat capacity by the number of moles in the reaction
how do we measure reversible expansion at a constant temp
๐บq(rev) = -๐บw(rev) = nRT ln(Vf/Vi)
๐บs = ๐บq/T
we can find ๐บs even if the expansion is not done reversibly bc S is a state function
what does the ๐บs of surroundings depend on
depends on conditions
the answer for ๐บs for surroundings will be the opposite answer to the ๐บs of the system.
how do we find nr when using entropy of expanding idea gas.
use the ideal gas equation::: pv/T = nr
then use this in the gas expansion equation ๐๐