Thermo dynamics (Gibbs Free E)
In a system undergoing adiabatic compression, what are the values of internal energy and heat if work done on the system is 500 J?
Internal energy is 500 J and heat is 0 J.
Does enthalpy = Q?
It can at a certsain condition. When pressure is constant
ENtropy and its equation?
Measure of spontaneous dispersal of E @ specific temp ∆S=∆q/T
Isobaric
Pressure stays constant
What is the third law of thermo
The entropy of a system becomes zero as the systems tempature reaches absolute zero
WHat happens at boiling point?
Vapor pressure of solution = atompheric pressure
What is the first law of thermo
internal energy of a system is equal to the heat added to the system and work done by the system
adiobatic
no heat exchange ∆U=-W
What can be calculate at standard state?
∆G⁰ ∆H⁰ ∆S⁰
Std heat of Reaction equation (can also be of formation elements to compund)
∆Hrxn= ∆Hp-∆Hr
Process can be characterized single constant property
1. Isothermal 2. adiabatic 3. isobarric 4. isovolumetric
What is the heat energy required to completely vaporize 10 gof water beginning at 0°C? (The heat capacity of water is 4.2 J/g⋅K and the ΔH of water is 2260 kJ/kg. 4.9 Kj 26.8 Kj 228.1 KJ 2126 Kj
26.8 Kj
WHat are standard conditions and how do they differ from STP
293K @ 1 atm of 1M STP= 273K @ 1atm
Relationship between free E, Keq, Q?
At std state ∆G⁰ = -RTln(Keq) but outside of std state ∆G=RTlnQ/Keq Q<Keq ∆G<0 Q>Keq ∆G>O
Isothermal
Stays at constant temp. Q=W
what measures heat capcity of liquid
caliometer
Calc enthalpy for C (s) +2H₂O (g) --> CH₄ (g)
p-R C-H 4X415 =-1660 (forming) - C(s) --> C(g) = +2X H-H (436)=872 1587 73kj
how many laws of thermodynamics are there?
4
Heating curves and Q
At tempature changes (at a phase) use q=mc∆T At phase changes(s->L) use q=m∆Hmelt
WHats bond dissociation E?
E needed to break (endo) bonds Kj/mol of broken bonds
WHat has a higher activation energy endergonic or exergonic?
Endergonic has a much higher acitvation energy ()
WHats Fusion(melting)? Whats the opposite?
Happens when phase change goes from solid to liquid
A hot object is placed next to a cold object so that they are touching. Which of the following statements is true? I. Heat will transfer from the hot object to the cold object because the hot object has a higher temperature. II. The two objects are in thermal equilibrium III. Internal energy will transfer from the hot object to the cold object because the hot object has greater internal energy.
Only I II is wrong because Heat will transfer not internal energy
Additional gas is pumped inside a rigid container that stores compressed gas. Which of the following is a true statement about this system? Choose 1 answer: The molar concentration of gas is decreasing. The volume of the container is decreasing. Pressure is constant throughout the compression. There is no work done on the container.
P=NRT/V W=P∆V since W=+ work is being done on the sys not on container There is no work done on the container.
WHat is heat capcties
Substance can have same specfic heat (amount of hear rq to raise temp by 1 dergree) Difference is by substance mass MC
True or false? Hess's Law states that the energy change of a process is independent of the path that was taken to get there
True.
Isovolumetric
Volume stays constant
WHats is a state function? Are they pathway depdent or indepdent? whhat are some state functions?
describes physical characteristics at equilibrium Independent T,P,S,H,G, V, density, ∆U
WHat are path functions?
describes physical characteristics depend on path taken Work and Heat
Hess's Law is true for variables such as enthalpy and entropy because these are _________ Variables. (A) Process (B) State (C) Fixed (D) Variable
B State
Whats work equation W=+ W=-
W=P∆V Work on the system Work by the system
How does a body overcome a nonspontenious reaction?
it overcomes by COUPLING it with a spontaneous rxn.
What is the net work done on the gas as it goes from point C to D and then to E on the Pressure vs Volume diagram?
First find W=P∆V(f-I) ∆U=Q-W
Whats the Zeroth law of thermo
For something to be in thermo equilibrium it must be the same temperature Delta U =
Entropy and phases boundries?
Freezing decrease entropy Boiling increase entropy sublimination increase the most entropy THink about microstates
WHats happens to Q at a phse change?
HEat stays constant because energy is being absorbed to break intermolecular bonds
whats sublmination?
Happens when going from Solid to gas depostion
Whats Vaporization?
Happens when phase change goes from liquid to gas Temp decreaasesas vaporzation happens bc its endo thermic condensation
What is enthalpy?
Heat exchange at a constant pressure ∆H + endothermic ∆H - exothermic
Tempature vs Heat
Heat is E transfer due to differences in tempature Tempature is Average kentic E of a substance
Equal amounts of heat are absorbed by 100 g samples of various solid metals with differing specific heat values. Which of the following statements is true regarding metals and their specific heat values? The metal with the smallest specific heat will undergo the smallest change in temperature. The metal with the greatest specific heat will resist melting to a greater degree at its melting point. The metal with the greatest specific heat will undergo the smallest change in temperature. The metal with the smallest specific heat will resist melting to a greater degree at its melting point.
Q/m∆T=c The metal with the greatest specific heat will undergo the smallest change in temperature.
What does hess law state? Whats it's importance?
State functions like ∆H or ∆G∆S of reaction are additive. energy change of a process is independent of the path that was taken to get there combine reactions and add or subtract their ∆H
When heating a solution, a scientist detects a temperature increase in the solution during a period of time. Which of the following statements accurately characterizes the solution during this period? The velocity of molecules in the solution is increasing. The solution's temperature increase is proportional to its ΔH_{vaporization}ΔH vaporization The solution is at boiling point. The solution is undergoing a phase change.
The velocity of molecules in the solution is increasing. T stays constant at phase schnages
Whats is the second law of thermo
energy spontaneously disperses from localized area to dispersed if not hindered. Delta s will be +
WHat is gibbs free energy and equation?
measure ∆H and ∆S as system undergoes process . tells us whether a system is spontenous or not (nothing about its rate) ∆G=∆H-T∆S
Cup with 80g of H₂O @ 300K mixed into a cup of 200g H₂O @ 450K. whats the equlibrium temp?
q=q- mc∆T=-mc∆T 80g (1j/g*k) (t₂-300K)=-(200 1 (T₂-450) T₂=400K
open system
A system that can exchange matter and energy
what is a closed system
A system that can't exchange matter but can exchange energy
what is an isolated system
A system that can't exchange matter or energy
Phase changes?
Charectistics @ different temps or pressures Solid Liquid Gas
