Exam 1 – Pollard

The enthalpy is ________ when a A-A reactants form A-B products.
negative
The entropy is ______ when there are more moles of gas on the reactant side than product side.
negative
What are the 3 things to look for when determining entropy?
1. moles of gas (which side has more?)
2. complexity of products/reactants
3. size/mass of compounds
The enthalpy is ___________ when A-B reactants for A-A products.
positive
The entropy is ___________ when a complex/larger reactant forms a simpler/smaller product.
negative
The enthalpy is ____________ when breaking ionic compounds.
positive
The entropy is ___________ when the reactants form gaseous products.
positive
If a chemical reaction results in ONLY a phase change, do the enthalpy and entropy have the same or opposing signs?
Same.
How do you find the percent yield of a reaction?
(experimental yield/theoretical yield) X 100
A reaction is spontaneous when its change in Gibbs free energy is ___________.
negative
A bond is _______ and less stable when it has _______ potential energy.
weak; high
Breaking bonds __________ energy while forming bonds ________ energy.
requires; releases
Exothermic processes are ________ energetically stable.
more
The ________ stable the products, the more likely the reaction to proceed to ___________. (____________)
more; completion; extent
If the enthalpy is negative, then the process is ___________.
exothermic
Exothermic processes energetically favor _________.
products
If the enthalpy is positive, then the process is ____________.
endothermic
Endothermic processes favor _____________.
reactants
The stronger the intermolecular forces, the more ____________ the enthalpy.
negative
Based on Coulomb’s Law, one may expect forces between ions to be stronger in these 2 scenarios:
1. the larger the charge of the ions (larger q’s)
2. the smaller the size of the ions (smaller r)
The higher the entropy, the ________ configurations in a system.
more
A phase change goes from solid to liquid, from liquid to gas. Thus, the process is ____________.
endothermic
A phase change goes from a gas to liquid, from a liquid to solid. Thus, the process is ____________.
exothermic
Chemical reactions in which the total entropy of the products is higher than the total entropy of the reactants are entropically __________.
favored
These 3 descriptions point towards a reaction that is entropically favored (entropy > 0).
1. fewer constraints
2. larger molar mass
3. more complexity
___________ are dominant factors for entropy.
Gases
Is favorability of a reaction temperature controlled?
No.
The more negative the Gibbs free energy is, the __________ the extent of the reaction and the more thermodynamically stable the ___________ than the ____________.
larger; products; reactants
What is the Gibbs free energy equation?
G = H – TS
What is the 2nd Law of Thermodynamics?
At constant T and P, G < 0 for thermodynamically favored processes.
The Gibbs free energy equates to ____ for elements in their standard state.
0
Chemical reactions tend to reach an ______________________ in which the concentration of products and reactants does not vary over time.
equilibrium state
Product-favored process: G < 0, K ___ 1
Reactant-favored process: G > 0, K ____ 1
>; <
x

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