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
