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Chem 1020 Test 1.
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Exam of 18 pages for the course Biology 101 at Biology 101 (Chem 1020 Test 1.)
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Chem 1020 Test 1What happens in a spontaneous reaction? - ANS-the total entropy of the universe must
increase.
Change in Free Energy - ANS--tells position and direction of a reaction
-easier to calculate than entropy
1st law of thermodynamics - ANS-the energy of the universe is constant. (any energy
lost by system is gained by surroundings and vice versa)
2nd law of thermodynamics - ANS-the entropy of the universe increases in any
spontaneous process
3rd law of thermodynamics - ANS-the entropy of a perfectly ordered crystalline
substance at 0 K is 0.
entropy - ANS-a measure of how dispersed (Random) the energy in a system is at a
specific temperature
Gibbs free energy equation - ANS-ΔG = ΔH - TΔS
Why is free energy important? - ANS-shows when a reaction is spontaneous
Exothermic Reaction feels... - ANS-hot (reaction gives off heat and surroundings get
warm)
Endothermic reaction feels... - ANS-cold (reaction takes in heat and surroundings get
cold)
equation of energy - ANS-delta E= w + q
-since energy is neither created nor destroyed, the energy of the system must equal the
work done on or by the system plus the heat gained or lost by the system
Work equation - ANS-w=-PdeltaV
What happens to volume when work is done on system? - ANS-When work is done on
system (+) the volume contracts (less gas) and surroundings are larger
,What happens to volume when work is done by system? - ANS-When work is done by
system (-) the volume expands (more gas) and the surroundings are smaller
If heat enters system - ANS-q (+), endothermic (cold surroundings)
if heat leaves system - ANS-q (-), exothermic (hot surroundings)
spontaneous reaction - ANS-proceeds on its own without continuous external influence
under a given set of conditions
-may need a spark to initiate
-ex: diamond conversion to black carbon, rusting, combustion, cold pack reaction
non spontaneous reaction - ANS-only proceeds in the presence of a continuous
external influence
If a process is spontaneous in one direction... - ANS-...it will be non-spontaneous in the
other (irreversible)
How does sign and magnitude of enthalpy change affect spontaneity? - ANS-sign and
magnitude of enthalpy change affect but do not determine spontaneity
how is spontaneity determined? - ANS-spontaneity is determined by comparing the free
energy of the system before and after the reaction
-spontaneous reactions move systems towards a lower free energy position
-always moves toward a state of lower energy (more stable state)
enthalpy - ANS-a measure of the total energy of a system; the sum of the internal
energy and the pressure volume product of a system
Positive entropy is likely to be? - ANS-Spontaneous!
Delta S universe= Delta S system + Delta S surroundings >0
Entropy changes with: - ANS--increasing temp (high temp= moving faster)
-increasing volume (more room to move)
-increasing number of independent particles (more collisions/ stuff)
-changes of state (particle organization)
-molecular structure (more bonds= more moving parts)
What is the temperature where all molecular motion ceases and entropy = 0? -
ANS-absolute zero
, Delta H of native elements - ANS-0
Delta S of native elements - ANS-non- zero
What does more bonds mean for entropy? - ANS-More bonds = larger molecule= higher
entropy
In general, entropy of the same substance (phases)? - ANS-gas>liquid>solid
allotrope - ANS-different arrangements of atoms- have different absolute entropies
Delta S equation - ANS-S products - S reactants
S final - S initial
state function like enthalpy
Delta S + - ANS--increase in energy dispersion (faster, move more, less organized)
-Endothermic
-When a molecule breaks into multiple pieces (break bonds)
-decrease pressure/ increase volume
Delta S - - ANS--decrease in energy dispersion (slower, move less, more organized)
-exothermic
-increase in number of gaseous molecules (create bonds)
-increase pressure/ decrease volume
Dissolution involves 2 parts to the entropy change! - ANS-1. entropy decreases as
solvent molecules arrange themselves around the ions (solids containing highly charged
ions aren't soluble in water)
2. entropy increases as the lattice is broken (entropy of mixing)
The amount the entropy of the surroundings changes depends on the temperature it is
at originally. The higher the original temperature... - ANS-the less effect addition or
removal of heat has
The amount the entropy of the surroundings changes depends on the temperature it is
at originally. When heat is added to surroundings that are cool... - ANS-it has more of an
effect on the entropy that it would have if the surroundings were already hot
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