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Apologia Chem M13B

Thermodynamics - Module 13 B

QuestionAnswer
Standard enthalpies of formation can be either positive or negative.
The enthalpy of formation depends upon the __________ of the substance. state
The heat released by a reaction that makes gaseous water should be ________ than the heat released by a reaction that makes liquid water. less
Σ summation
When we are finding the ΔH° of any reaction, it is important to use the PRODUCTS minus the REACTANTS.
IF you have the ΔHf° of the elements involved in their proper PHASE, always use __________________ to determine the ΔH. Hess's law
Use bond energies to determine ΔH ONLY if you don't have EVERY ΔHf° necessary to solve the problem OR if you don't know the PHASE of every substance in the reaction.
A reaction coordinate in an energy diagram tells us how close the reaction is to completion.
The big BUMP in an energy diagram represents the ENERGY of the INTERMEDIATE state of the reaction.
activation energy the energy necessary to start a chemical reaction
ALL reactions require a certain amount of activation ____________ to get the reaction started. ENERGY
Under normal conditions, molecules don't like to get close enough to rearrange their valence electrons because the electrons that must be rearranged REPEL each other.
In an energy diagram of an ENDOthermic reaction, the energy of the reactants is ____________ than the energy of the products. lower
A reaction that is EASY to get started has a ________ activation energy. low
the measure of disorder in a system, abbreviated with a capital S entropy
second law of thermodynamics The entropy of the universe must always either increase or remain the same; it can never decrease.
The entropy of a substance changes when the substance changes phase.
The solid phase has the ____________ amount of entropy associated with it. least
The entropy of the liquid state is higher than that of the ___________ state. solid
The entropy of the gaseous state is the ________________ of all the states. highest
In general, when a substance's temperature increases, its entropy increases.
The entropy of a system increases as the matter it contains increases.
Since it is difficult to measure the entropy of a system, chemists are usually more interested in the change in entropy that a system undergoes.
To determine the sign of ΔS for a chemical reaction, we look at the number of molecules or atoms on each side of the equation and the phases of the substances involved.
ΔS universe must be greater than or equal to 0.
In general, the side of a reaction that contains the most molecules or atoms in the ____________________ has the highest entropy. gas phase
If no gases are present in a reaction, the side that has the most molecules in the ____________________ has the highest entropy. liquid or aqueous phase
If all of the substances in a reaction are solids, then the side with the largest number of __________________ has the highest entropy. molecules
The S of an element is not 0.
Entropies are all __________________________ because all substances have some level of disorder. positive numbers
ΔS change in entropy, tells us about change in entropy of a REACTION
There are spontaneous processes that occur everyday as a result in a decrease of disorder.
The second law of thermodynamics doesn't disprove evolution, but it does attach some pretty strong conditions to it.
ΔG = Gibbs free energy, = ΔH - T x ΔS
If ΔG is LESS than 0, then the reaction is _______________ with the 2nd Law of Thermodynamics and IS spontaneous. consistent
If ΔG is GREATER than 0, then the reaction cannot proceed because it violates the 2nd Law.
ΔG is important because it takes inventory of all of the entropy of both the chemical reactions and its surroundings.
Gibbs free energy relates change in entropy (ΔS), change in enthalpy (ΔH), and temperature to tell us WHETHER or NOT a REACTION is consistent with the 2nd Law of Thermodynamics
enthalpy the energy stored in a substance
ΔH change in enthalpy, allows us to learn about the change in ENTROPY of a reaction's SURROUNDINGS
change in enthalpy the energy change that accompanies a chemical reaction
Created by: MrsHough
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