Chem Exam Review Flashcards
Define Exothermic
system transfers heat to surrounding. Temp increases, energy is released.
Endothermic
system absorbs heat from surrounding. Temp decreases, energy is gained.
How to calculate q[surroundings]?
q[surr]=mcΔT. +q = heat inc. -q = heat dec.
What is Enthalpy? How do you calculate it?
Heat content. ΔH[sys]=-q[surr]. + ΔH endo, - ΔH exo
How to calculate bond energy?
ΔH[rxn] = sum of reactant BE - sum of product BE
How to calculate molar enthalpy?
ΔH[sys] = n ΔH[x] *used also as conversion factor
How to calculate calorimetry with enthalpy?
n ΔH[x,sys] = -mc ΔT[surr]
Methods for Communicating Thermochemical Equations?
Energy term, Enthaply value, Molar enthalpy, Potential Energy diagrams
Energy terms and enthalpy value?
If e is reactant, rxn is endo. If e is product, rxn is exo. When enthalpy value is given (at end of equation) if + it is endo, if - it is exo.
How to calculate Standard Enthalpy of Formation?
ΔH = sum of nΔH[f,products] - sum of nΔH[f,reactants]
3rd Law of Thermodynamics
The S of perfectly ordered pure crystalline substance is 0 @ absolute zero. S = 0 @ T= 0K
How to calculate entropy?
ΔS = sum of nS[products] - sum of nS[reactants]
How to calculate Gibbs Free Energy?
ΔG = ΔH - T ΔS where S is in kj and T is in K.
ΔG = sum of n ΔG[f,products] - sum of n ΔG[f,reactants]
What is the meaning of G?
ΔG<0, rxn is spontaneous in Fwd direction.
ΔG>0, rxn is nonspontaneous in Fwd direction.
ΔG=0, rxn is @ equilibrium
How to calculate Reaction Rate?
Rate (r) = Δ[R/P] / Δt where R/P is reactant/product depending on whether consumption or production
What is the Rate Law?
[A] -> Products : r = k[A]^m
[A] + [B] -> Products : r = k[A]^m[B]^n where m and n are the rate order, and m+n = overall rxn rate order
What is the Transition State Theory?
Reactants transition to products with “enough energy”
What is Activation Energy?
(E[a]) The sufficient amount of energy needed to break bonds and overcome repulsive forces.
What is Collision Theory?
A successful collision is when there’s enough E[k] and the correct orientation.
