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27 Cards in this Set
- Front
- Back
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1st law of thermo dynamics
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The law of conservation of energy- energy can be converted from one form to another but can can be neither created nor destroyed
The energy in the universe is constant |
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Exothermic
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evolution of heat
energy flow out of system ex combustion |
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endothermic
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reactions that absorb energy from surroundings
heat flows into the system |
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Thermochemistry
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the study of the amount of heat in a chemical reaction
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Internal energy
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(U) the sum of kinetic and potential energies of the particles that make up the sample
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E _total_=
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KE+PE+U
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System
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the part of the universe that is the focus of the study
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Surroundings
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the parts of the universe that interact with the system
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U state function
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dependent on present state of system
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∆U=
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=U_final_ - U_initial_
=q+w (heat + work) |
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Any energy entering the system carries a _____ sign if heat is absorbed by the system, q>0 if work is done on the system, w>0
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positive
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Any energy leaving the system carries a _____ sign if heat is given off by the system, q<0. if work is done by the system w<0
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negative
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If more energy enters the system than leaves _____. if more energy leaves the system then enters ______
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∆U >0
∆U <0 |
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Heat
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transfer of energy between two objects due to a temperature difference
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q heat of rxn
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amount of heat absorbed or released during the chemical reaction
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Heat flows from a region of higher T to a region of lower T
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thermal equilibrium
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Heat reactions (q)
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+q=heat is absorbed by system
endothermic -q= heat is released by system exothermic |
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Enthalpy of rxn=
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=∆H=q_p_
(heat of reaction at constant pressure) |
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H=
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U+PV
U= internal energy P= pressure V= volume |
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∆H=
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H_product_ - H_reactant_
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Constant pressure ∆H=
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∆U + P∆V
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Enthalpy
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measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.
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Heat capacity (c)
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amount of heat needed to raise temperature of sample 1℃
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Heat associated with temperature change
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q=C x ∆T
∆T=T_f_ - T_i_ q=s x m x ∆T |
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Specific heat
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(s) amont of heat needed to raise temperature of 1 gram of substance by 1℃
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Hess's law
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The law states that the enthalpy change for a reaction that is carried out in a series of steps is equal to the sum of the enthalpy changes for the individual steps.
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standard enthalpy of formation
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is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 degrees Celsius). Its symbol is ΔHfO or ΔfHO.
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