Chem/Phys Study Concepts Flashcards
An isothermal process occurs when?
The systems temperature is constant. If U=0 then Q=W
An adiabatic process occurs when?
No heat is exchanged between the system an enviroment Q=0 then U=-W
An isobaric process occurs when?
The systems pressure is constant. Does not alter first law so U=Q-W
An isovolumetric process occurs when?
The system has no change in pressure. With no change in pressure W=O and U=Q
What are standard conditions for state functions?
25 deg C (298 K), 1 atm Pressure, 1 M concentration
What are the State Functions?
Pressure, Density, Temp, Volume, Enthalpy, Internal Energy, Free energy
Mneumonic for State Functions?
When I am under Pressure and feeling dense, I watch TV and get HUGS
What state change is vaporization?
Liquid to gas
What state change is condensation?
Gas to liquid
What state change is sublimation?
solid to gas
What state change is deposition?
Gas to solid
Enthalpy is?
the thermal energy of the substance
What is the symbol for Enthalpy?
H
What is the Q value for Endothermic Processes?
♦Q>0
What is the Q value for Exothermic Processes?
♦Q<0
What is Hess’s Law?
That since Enthalpy is a State function its not path-depended therefore all enthalpy changes in a rxn are additive.
H=H1+H2+H3….etc
What is the formula for the enthalpy of a reaction, when bond dissociation comes into play?
Hrxn=Sum H(bonds broken)-SumH(bonds formed)
Bond dissociations:
What is the energy of bonds dissociating?
What is the energy of bonds formed?
Bonds dissociation energy >0
Bond Formation energy <0
*Breaking bonds requires energy
Forming bonds releases energy
Combustion:
How do alkane reactant size effect number of combustion products?
The larger the alkane reactant=more numerous the combustion sizes
What is the definition of Entropy?
It is a measure of spontaneous dispersal of energy at a specific temp: How much energy is spread out, and how widley spread out energy becomes
What is the change in free energy?
The maximum amount of energy released by a process at a constant temperature and pressure that is available to perform useful work
What is the formula for Gibb’s free energy?
DeltaG=DeltaH-TDeltaS
Gibb’s Free Energy:
If DeltaG<0 the reaction is?
G<0 the reaction is spontaneous
Gibb’s Free Energy:
If DeltaG=0 the reaction is?
The rxn is at equilibruim
Gibb’s Free Energy:
If DeltaG>0 the reaction is?
The reaction is non-spontaneous
Delta G is ____________ ____________ when both delta H and delta S have the same sign.
Delta G is temperature dependent when both delta H and delta S have the same sign.
*The temp dependence is equal to the sign they have
Negative delta H and delta S are temp dependent at low temps.
Positive delta H and delta S are temp dependent at high temps
Gibb’s Free Energy:
What sign for Delta H and Delta S means the reaction is nonspontaneous?
A positive Delta H and a negative Delta S is a nonspontaneous reaction
How does Keq relate to Gibbs Free Energy?
A high Keq=more positive natural log=more negative delta G=more spontaneous rxn.
You have to switch equations for Delta G when a reaction is in progess, why?
Because once a reaction begins to progress, it is no longer in the standard state condition of 1M and the value must be replaced by another number that reflects its path towards equilibrium.
When a reaction is in progress for delta G, what variable is added to the equation?
What is the new equation
The reaction quotient Q.
Delta Grxn=DeltaGºrxn+RTlnKeq=RT(Q/Keq)
Keq and Gibb’s Free Energy:
How do ratios of Q and Keq affect whether a rxn is spontaneous or nonspontaneous
(Q<keq></keq>
<p>(<em>Q</em>>Keq)=Ratio>1=DeltaG>0=Reverse Spontanous</p>
<p>(<em>Q</em>=Keq)=reaction is at equilibrum=DeltaG equals 0</p>
</keq>
The saturation point of a compound is also known as the?
equilibrum point
What is the formula for Ksp?
AmBn(s)→mAN+(aq)+nBM-(aq)
With this in mind-
Ksp=[AN+]m[Bm-]n
Ksp is ________ and _________ dependent.
Temperature and pressure (for gasses only)
How does temperature affect Ksp values?
Higher temp=higher Ksp value
Lower temper=lower Ksp value
What is ion product?
how to tell where the system is in relation to equilibrum
How do Ion Product (I.P) and Ksp relate?
I.P<ksp></ksp>
<p>I.P=Ksp =equilibrium</p>
<p>I.P>Ksp = supersaturated</p>
</ksp>
When the I.P>Ksp and the solution is supersaturated, what occurs?
Precipitation because the solution is trying to get back to equilibrum
What is the formula for Ion Product?
With this in mind: AmBn(s)→mAn+(aq)+nBm-(aq)
Forumula for Ion Product is: I.P=[An+]m[Bm-]n
What are the steps in solving a molar solubility problem?
1) Write out equation
2) Use Ksp formula
3) Use x to figure out the amounts that dissociate
4) Plug x’s into Ksp equation
5) Plug in molar solubility
6) Simplify and reduce to proper SI notation
What are the molar solubility shortcuts?
MX=x2
MX2=4x3
MX3=27x4
Kf represents?
The formation constant: When aqueous ions find stability in an aqueous complex
What is the common ion effect?
Molar solubility is reduced by the presence of one of it’s constituent ions in solution
