thermodynamics Flashcards
energy cannot be created or destroyed during a chemical reaction
what happens to the energy in a reaction where high energy reactants form low energy products?
given out to the surroundings
endothermic or exothermic?
energy is given out to the surroundings during a chemical reaction
exothermic
what does all matter have?
mass
temperature
volume
entropy
what is entropy?
a measurement of disorder
who was entropy introduced by?
rudolf clausius
1865
what is the symbol of entropy?
S
what affect does higher temperature have on entropy?
higher entropy
more disorder
particles gain more kinetic energy
what happened to its entropy when a solid dissolves in water?
it’s entropy increases
what happens to the entropy when a single reactant breaks down into two or more products?
entropy always increases
entropy increasing and decreasing in terms of positivity and negativity
increased entropy- positive entropy change
decreased entropy- negative entropy change
what is the entropy change for the following reaction:
S8 —> 4S2
entropy change is positive
what is the entropy change if a reaction has more moles of product than reactants likely to be?
positive
what happens to entropy when there’s more possible configurations of the arrangement of kinetic energies ?
entropy increases
equation of entropy
S = k log (W)
S= entropy
W= number of configurations
k= a constant
log= the logarithm of
as W increases, S increases too
how is the simple system similar to a real life atomic system?
they both contain particles in boxes
their particles are both restricted to certain kinetic energies
you can’t measure the kinetic energy of each particle in either system
when we crunch the numbers, we find that changing state from
solid- liquid
or
liquid- gas
increases entropy
why is that?
there are more available kinetic energy levels for gases than liquids
there are more available kinetic energy levels for liquids than solids
entropy change equation
**
entropy change = q/T
units= J/K
q-heat
T-temperature
what is the entropy of all substances at 0 K?
0 J/K
why is the entropy of a substance 0 at 0K?
the particles are not moving
the particles have no disorder
for any substance, a graph can be made of how it’s entropy changes with temperature. what do these graphs show?
start at the origin
show that entropy increases with temperature
have a large jump at the melting point of the substance
have a large jump at the boiling point of the substance
standard molar enthalpy definition
the entropy of 1 mole of a substance at 298K
units for the entropy change of a reaction
J/K/mol
for any chemical reactions what are the surroundings defined as?
anything which isn’t in the reaction equation
what do exothermic reactions do to their surroundings?
increase the entropy of their surroundings
what do endothermic reaction do to their surroundings?
decrease entropy of their surroundings
what effect will a negative entropy change of a reaction have on the surroundings?
the entropy of the surroundings will increase
the entropy of the surroundings will be positive
entropy change of surroundings
equation
-entropy change of reactions/ temperature
units for entropy change of surroundings
kJ/K/mol
what do you do to convert from
kJ/K/mol to J/K/mol
x1000
what do you work out if we add the entropy change of a reaction system and the entropy change of the surroundings?
the entropy change of the universe
what is the reason a chemical reaction can happen because of?
it increases the entropy of the universe
what do we say instead of saying the entropy change of the universe will or won’t happen?
we say it is feasible or not feasibke
what must happen for a reaction happen?
occur at reasonable rate
increase the entropy of the universe
why do some reactions not happen when scientists mix the reactants in a lab?
the activation energy for the reaction is too high
the rate of reaction is too slow
1 st law of thermodynamics
energy cannot be created nor destroyed
2nd law of thermodynamics
for any process to happen, it must increase the entropy of the universe
for a reaction to be feasible what must gibbs free energy change be ?
negative
gibbs free energy change
equation
gibbs free energy change =
-T (entropy change of the universe)
change in gibbs free energy busing different types of entropy
equation
delta G= change in enthalpy of a reaction- change in Temperature x entropy change
