Thermodynamics & Calorimetry

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Chemistry

Thermodynamics

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49 Terms

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Collision Theory
reactants need to combine w/ enough energy and in proper orientation in order to react
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effective collision
a collision that results in a chemical reaction
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law of conservation of energy
energy cannot be created or destroyed
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kinetic energy
energy used for motion
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potential energy
stored energy- when reactants collide
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activated complex
unstable phase while reaction is occurring
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enthalpy
the amount of energy(heat) being stored in bonds of a compound.

Note: products & reactants almost always have an absorption release of enthalpies
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endothermic reaction
* when products have a higher enthalpy
* reaction in which energy is absorbed
* when products have a higher enthalpy * reaction in which energy is absorbed
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exothermic reaction
* reaction in which energy is released
* when products have a lower enthalpy
* reaction in which energy is released * when products have a lower enthalpy
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specific heat
substance ability to resist temperature change
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high specific heat
requires a lot of energy to inc. or dec. in temperature
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Calorimetry Equation
mcΔT
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Q
heat (joules)
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M
mass (grams) \*if not in grams, convert
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C
specific heat (j/gC)
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T
temperature (C)
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reactants
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1
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products
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6
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activation complex
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3
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Heat of the reaction
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5
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Q of absorbed
Q of released =
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Q of released
Q of absorbed =
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\-Q
if energy is lost (__Q)
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\+Q
if energy is absorbed (__Q)
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ΔH (delta H)
change in variable

H final-H initial
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\-ΔH
exothermic H
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\+ΔH
endothermic H
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potential energy (hold together)
there is a specific amount of energy holding together H2 & O2
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potential energy
When the particles collide, Kinetic Energy becomes ______
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5 things to increase rate of Effective collision
* temperature (changes energy & likelihood, speed & rate)
* pressure (decrease in volume, more collisions)
* surface area (increase # of particles for collisions)
* presence of catalyst
* concentration (likelihood of collisions is higher bc more molecules)
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no, sometimes they bounce off because:

* not enough energy
* did not collide in the right spot
Do molecules always react when they collide?
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they collide
why do molecules react?
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entropy
the amount of disorder in a system

naturally increases (easier to create disorder than order)
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least entropy
particles in solids stay in place: rigid, fixed shape, fixed volume (____entropy)
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most entropy
gas particles move freely & randomly (____ entropy)
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least particles
least disorder (solid)
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most particles
most disorder (gas)
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S
entropy
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entropy equation
ΔS = S final - S initial
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spontaneous
* uses energy to create reaction
* once reaction starts, continues on own
* these reactions can possibly take a long time
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non spontaneous
* needs a constant source of energy
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\-ΔG
spontaneous reaction
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which thermic is more favorable
exothermic (more spontaneous)
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which ΔS is more energetically favorable
\+ΔS
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\+ΔS
inc. in entropy
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\-ΔS
dec. entropy
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Exothermic + inc entropy (-ΔS) =
ALWAYS SPONTANEOUS
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Endothermic + dec. entropy =
NEVER SPONTANEOUS
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gibbs free energy equation
ΔG = ΔH - TΔS