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Delta S>0
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Spontaneous reaction
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Delta S<0
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Not spontaneous (will not happen in the natural world)
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Delta s=0
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Equilibrium. Reaction can occur in any direction under stated conditions
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Delta U = ?in adiabatic process
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Delta U = w
depends on initial and final statesno temperature exchange so q=0internal energy depends on T |
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W = ?(isothermal process)
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W = -nRT ln (V2/V1)
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W = ?(isobaric process)
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W = -Pdelta V
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W = ?(isochoric process)
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W = 0no change in volume
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Irreversible work
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W = -Pext delta V
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Reversible
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A process is reversible if at every stage the direction of change can be reversed by making an appropriate infinitesimal change in the temperature pressure or some other property of the surrounding. (to get maximum work)
w = -nRT ln (V2/V1) reversible isothermal expansion |
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Internal is decreased/increased in expansion?
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Decreased. It is lowered by the amount of work that appears in the surroundings. Internal energy of an ideal gas depends on T
U=3/2 RT --> R is constant Increase in U = increase in T |
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Cools or heats up?
1. adiabatic expansion2. adiabatic compression |
Expansion: coolsCompression: heats up
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Why does it rain more in Santa Cruz than Palo Alto?
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In order for the air to cross the mountains, it adiabatically expands upward, raising the air above it and doing work. Since delta U = w, w is negative, energy (delta U) of the gas decreases. --> gas cools down. air at low temps can't hold moisture, so it precipitates.
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Delta U = ?Closed system
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Delta U = q + w
w= work done on systemchanges energy with the surrounding |
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Work done (+/-)1. received by system2. done by system
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1. + : work/heat received by system2. - : work/heat done by system
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Delta U = ?change in state to a state of the same energy
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Delta U = 0delta U = 0 = q + wq = -wisothermal process!
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