L2: Thermochemistry Flashcards
What is the first law of thermodynamics?
The law of conservation of energy.
Energy is not created nor destroyed, the energy of the universe is constant.
What is internal energy (E)?
The sum of the kinetic and potential energies of all the particles in the system. I can be changed by a flow of work, heat, or both.
What is the second law of thermodynamics?
Entropy will always tend to increase. Heat will always flow from from higher to lower temperature
What is the third law of thermodynamics?
Entropy is temperature-dependent. If all the thermal motion of molecules (kinetic energy) could be removed, a state called absolute zero would occur.
Absolute zero is 0 K or -273.15°C
The gas in a piston is warmed and absorbs 670 J of heat. The expansion performs 350 J of work on the surroundings. What is the change in internal energy (E) for the system?
+320 J
If the Gibbs value for a reaction is +ve, is the reaction feasible?
No
If the Gibbs value for a reaction is -ve, is the reaction feasible?
Yes
What is the formula for calculating Gibbs energy?
deltaG = deltaH - TdeltaS
deltaH is positive, delta S is positive.
Is this reaction feasible?
At low temperatures, deltaG would be positive, so the reaction would not be feasible.
At higher temperatures, deltaG would be negative, so the reaction would be feasible.
This reaction is feasible only at higher temperatures.
deltaH is positive, deltaS is negative.
Is this reaction feasible?
This reaction will never be feasible.
deltaG will always be positive.
deltaH is negative, deltaS is positive.
Is this reaction feasible?
This reaction will always be feasible.
deltaG will always be negative.
deltaH is negative, deltaS is negative.
Is this reaction feasible?
At lower temps, deltaG can be negative, making this reaction feasible.
At higher temps, deltaG would be positive, making this reaction not feasible.
This reaction will only be feasible at lower temperatures.
