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58 Cards in this Set
- Front
- Back
First law of thermodynamics? |
energy can be converted from one form to another but energy cannot be created or destroyed |
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Potential energy? (PE) |
due to position or composition |
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Kinetic energy? (KE) |
due to motion of object |
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Symbol for heat? |
(q) |
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Heat is the |
energy transferred between samples because of difference in temperatures |
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Amount of energy transferred is measured in ? |
Joules (J) |
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Heat _____ be measured ___________ so __________ is used to track transfer of _______ |
cannot, directly, temperature, heat |
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2 ways to transfer energy ? |
1. heat (q) 2. work (w) |
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Calorimetry is the process of |
measuring energy changes |
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Calorimetry requires an ____________ system |
isolated |
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Open system? |
both matter and energy can enter/escape |
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Closed system? |
matter cannot but energy can enter/escape
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Isolated system |
neither matter nor energy can enter/escape |
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In a calorimeter the energy given off during a reaction equals the |
energy absorbed by water [qabsorbed = qreleased] |
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symbol for specific heat capacity? |
(c) |
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symbol for heat capacity? |
(C) |
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SHC is |
amount of heat (q) required to raise temp. of 1g of the substance by 1 degree C |
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HC is |
amount of heat required to raise tmp. of given quantity (m) of substance by 1 degree C |
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Change in temp = |
Tfinal - Tinitial |
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what is the SHC of water? |
4.19 J/gC |
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symbol for enthalpy is |
H |
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enthalpy is |
heat given off/absorbed during a reaction at constant pressure |
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change in enthalpy = |
Hproducts - Hreactant |
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Exothermic (5) |
- (-) - Hp < Hr - energy produce IN reaction - flows OUT of system - container FEELS HOT |
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Endothermic (5) |
- (+) - Hp > Hr - energy CONSUMED by reaction - flows INTO system - container FEELS COLD |
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change in enthalpy = |
heat supplied |
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RC IS |
reaction coordinate // time |
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characteristics of exothermic reactions
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- energy produced in reaction
- flows OUT of system - container feels HOT to touch |
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characteristics of endothermic reactions
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- energy consumed by reaction
- flows INTO system - container feels COLD |
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molar enthalpy
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enthalpy change in chemical system per mole of specified chemical under change
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change in enthalpy of system is equal to
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change in thermal energy of the calorimeter
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4 WAYS OF COMMUNICATING ENERGY CHANGES
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1. MOLAR ENTHALPY
2. ENTHALPY CHANGE 3. TERM IN BALANCED EQUATION 4. CHEMICAL POTENTIAL ENERGY DIAGRAM |
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METHOD 1
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Molar Enthalpy EXO: Delta r H m < 0ENDO: Delta r H m > 0 |
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METHOD 2
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Enthalpy Change EXO: reactants -> products; delta r H < 0ENDO: reactants -> products delta r H > 0 |
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METHOD 3
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Term in Balanced Equation
EXO: reactants -> products + energy ENDO: reactants + energy -> products |
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METHOD 4
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Chemical Potential Energy Diagram
EXO: Ep (reactants) > Ep (products) ENDO: Ep (reactants) < Ep (products) |
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LABEL Q=mc🔺t |
Q= energy/heat m= mass C= Specific heat capacity t=temp change |
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Label Q = c🔺t
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Q = energy/heat c= heat capacity t= temperature change |
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mass in Q=mc(delta)t can also be |
Volume |
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Q system = |
- Q surroundings |
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(Delta)rH = |
Q |
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m(system)c(system)🔺t(system)= |
-(MwCw🔺Tw) |
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(Delta)rH = |
Q |
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mc(delta)t = |
n x (delta)rHm |
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(delta)rHm is measure in |
kJ/mol |
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(Delta)rH is measured in |
kJ |
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RULES FOR HESS' LAW (5)
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1. Write net reaction equation, if not given
2. Manipulate the given equations so they will add to yield the net equation 3. Multiply, divide and/or reverse the sign of the enthalpy of reaction 4. cancel and add the remaining reactants and products to yield the new equation 5. Add enthalpy changes to obtain the net enthalpy change |
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Reaction rate depends on (3)
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1. collision frequency
2. probability or orientation factor 3. activation energy (Ea) |
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making bonds
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releases energy (exo) `
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breaking bonds
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absorbs energy (endo)
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bond formation
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(-BDE) releases energy (exo)
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bond breaking
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(BDE) requires energy (endo)
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homogenous catalyst
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catalyst works by increasing chances that 2 molecules will positioned in the right way for a reaction to occur
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heterozygous catalyst
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First step: absorption (binding of reactant molecules to catalyst surface)
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catalytic converter
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promotes combustion using catalyst
GOAL: to release N2, O2, CO2 |
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some calorimetry assumptions
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1. all energy lost or gained by the chemical system is gained or lost respectively by the calorimeter (total system is isolated)
2. all the material of the system is conserves; that is, the total system is isolated 3. the specific heat capacity of water is 4.19J/gC 4. the thermal energy gained or lost by the rest of the calorimeter (other than water) is negligible, that is, the container, lid, thermometer, and stirrer do not gain or lose thermal energy |
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1mL =
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1g
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Combustion is a __________ reaction
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exothermic
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