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Reactions that are thermodynamically very favorable often proceed _____ than do less favorable ones. Conversely, some reactions are ______ than others even though they result in a comparatively less _____ product.
A transformation that yields the most stable products is said to be under ________ control. A reaction in which the product obtained is the one formed fastest is said to be under _____ control
- thermodynamic control
- kinetic control
A favorable energy change is one in which the ______ content of a system ______. Energy tends to flow from systems off ______ energy content to those with _______ energy content, like a hot oven cooling off when opened.
All chemical reactions are ______ and reactants and products interconvert to various degrees. When they aren't doing so, the reaction is said to be at _______.
When can we say the reaction goes to completion? What do w do with the arrow indicating the reverse reaction?
- When equilibrium lies extensively (more than 99.9%) on the product side
- We omit it, and consider the reaction irreversible for practical purposes
How do you find the equilibrium constant K? and what are the units
- [products]/[reactants] = K
- mol L-1
A _____ value for ___ indicates that a reaction goes to completion, it is said to have a large ______ _____
If a reaction has gone to completion, a certain amount of energy has been ______ and equilibrium constant can be related to the thermodynamic function called the ______ ______ ______ ______ change. What is the equation (2) and units of that change? What is the value of R?
- Gibbs standard free energy change
- ΔG = -RTlnK = -2.303(RT)(logK) *in kcal mol-1 or kJ mol-1R= 1.986 cal*K-1mol-1 or 8.3145 JK-1mol-1
If gibbs standard free energy change is negative energy has been _____. Large equilibrium constants indicate a ______ favorable ______ _______ _____. What is the equation for free energy at room temp 298K?
- free energy change
- ΔG = (-1.36)logK in kcal mol-1
Gibbs free energy equation as it relates to enthalpy change and entropy change
ΔG = ΔH - TΔS
Enthalpy changes in chemical reactions relate mainly to differences the ________ of the _______ in the products compared to those in that of those in the _______
Finding change in enthalpy with bond dissociation energies DH°.
ΔH = Sum of DH° of bonds formed - DH° of bonds broken
If ΔH is negative the reaction is ________ and the bonds formed are _______ than those broken. If ΔH is positive the reaction is _______.
Instead of applying entropy as disorder in scientific situations (not always quantifiable), we use it to describe changes in _____ _____. Because of the negative sign in front of TΔS in the ΔG equation, a positive value for change in entropy makes a ______ contribution to free energy. In other words, going from ______ to _____ energy dispersal is more thermodynamically favorable
- energy dispersal
- lesser to greater
When asked at what temp does a reaction become favorable, we set ΔG to ______ because that is the crossover point
In many organic reactions, the change in entropy is small, and it often suffices to only consider the changes in ______ ______ to estimate spontaneity. In these cases we equate ΔG to ___
Why do very spontaneous reactions, like the combustion of methane, occur so slowly?
During the course of the reaction, energy changes in the manner of a potential energy diagram like this:
A potential energy diagram plots energy as a function of ______ ______ which we measure by the ______ _____.
- reaction progress
- reaction coordinate
The reaction coordinate describes the combined processes of ______ _____ and _____ ______ that lead to the overall change in structure of _____ and _____
- bond breaking and bond forming
- reactants and products
Energy content being mapped in a potential energy diagram hits a maximum point called the _______ ______ before decreasing to the final value, which is the energy content of the ______ _______.
- transition state
- product molecules
The energy of the transition state may be viewed as a ______ to be overcome in order for the reaction to take place. The energy input required to raise the energy of the starting compounds to that of the transition state is called the _______ _____ (__) of the reaction.
- activation energy (Ea)
The transition state for methane combustion is very high in energy, so it has a large _______ _____ which equates to a very _____ rate
- activation energy
- slow rate
Molecules have _____ ____, energy resulting from their motion, however, it is often not enough to overcome the activation energy barrier. How do molecules make up for this deficit in energy?
- kinetic energy
- By colliding with each other and the walls of their containers, each collision transfers energy between molecules
The shape of the Boltzmann curve or potential energy diagram can also depend on _______. When it is high, kinetic energy is ______ and activation energy is ______ to defeat
A + B → C
In the reaction above, increasing the concentration of either A or B increases the _____ of the ______. What is the equation for the rate?
- rate of the reaction
- Rate = k[A][B] mol*L-1s-1
Rate constant K is the rate of the reaction at _____ ______ _____ of the two reactants A & B
1 molar concentration
The Arrhenius equation describes how _____ of reactions with different activation energies vary with ______. State the equation (2)
- K = Ae-Ea/RT = A(1/eEa/RT)
With regard to the Arrhenius equation, the higher the Ea, the _____ the reaction and the higher the temperature, the ______ the reaction
Why is it accurate to say that K is almost equal to A
A, the frequency factor or pre-exponential factor can be imagined as the maximum rate constant that the reacion would have if every molecule had sufficient collisional energy to overcome the Ea. This occurs at very high temps when Ea/RT is close to zero and e-Ea/RT is close to one
Contributions to enthalpy changes stem mainly from variations in ______ _____; contributions to entropy changes arise from the ______ _______ of energy in reactants and products. Entropy and enthalpy may describe the position of an equilibrium, but the rate at which it is established depends on the _______ of reactants and the ______ _______ separating ______ and reactants.
- bond strengths
- relative dispersal
- activation barrier
Bonds consist of ______ and chemical change is defined as a process in which bonds are _____ & _____. Therefore, when chemistry takes place, ______ move.
- broken & formed
A curved arrow (↷) shows the flow of a(n) ______ ______, (usually a(n) _____ ____ or a ______ _____) from its origin to its destination
- electron pair
- lone pair
- covalent bond
Name the general types of electron movement
- dissociation of a polar covalent bond into ions
- formation of a covalent bond from ions
- substitution reactions (simultaneous making of a bond while another is broken)
- addition reactions (involve double and triple bonds)
In dissociation of a polar covalent bond, the direction in which the pair of electrons moves depends on which of the two atoms is more ________. A↷B → A+ + :B-
The one that receives the electron pair becomes an ______ and the one that loses the electrons becomes a ______. Arrow always goes from _____ to _____ atom
In the formation a covalent bond from ions, we combine a ______ and ______. The curved arrow always goes from ______ _____ to ______
- cation and anion
- electron pair
In substitution reactions, the atom receiving electrons is said to be ________ and the one given up or sharing electrons to form a bond is said to be _______. We never draw the arrows in facing _____ _____, rather they flow in the ______ _____
- each other
- same direction
In addition reactions, movement of a lone pair toward an atom with a ______ or ______ bond. What is the result?
- double or triple bond
- formation of a new bond
- demotion from double or triple to single or double bond