CH 19 Chemical Thermodynamics and Ch 20 Electrochemistry

Entropy is the measure of the number of _available to the components of a system

energetically equivalent states

what is related to the third law of thermodynamics?

entropy

arrange solid, liquid, and gas according to the average kinetic energy of the molecules. (from high to low)

gas>liquid>solid

how entropy change is calculated and why?

- As a state function, entropy change, ΔS, depends only on initial and final states. -Although the sign of the entropy change can be predicted as described above, the actual value of ΔS∘ must be calculated from the absolute entropy values, S∘, of the reactants and products: ΔS∘=S∘(products)−S∘(reactants)

_ are two factors that impact melting points. explain how

-Molar mass and intermolecular forces -Heavier molecules require more energy to break away from their neighbors. Molecules experiencing stronger intermolecular interactions also require more energy to break away. Dipole-dipole interactions, experienced by chloromethane, are significantly stronger than London dispersion forces.

what is the relation between E∘ and K? what these two relations indicate?

-When E∘>0 and K>1 the reaction favors the products. -When E∘<0 and K<1 the reaction favors reactants.

The following conditions usually result in an increase in entropy: (3)

-a change of phase: solid→liquid→gas, -an increase in the number of gas molecules, or -a solid dissolving to form a solution.

characteristics of a irreversible process (2)

-a process in which the surrounding cannot be restored to their original state after restoring the system -spontaneous process

characteristics of a reversible process (2)

-a process in which the system and its surroundings can be restored to their original state by exactly reversing the change -process that reverse direction when an infinitesimal change is made

Molecular systems tend to move spontaneously to a state of maximum _(think about degree of order, how called, symbol)

-randomness or disorder. Molecular randomness, or disorder, is called entropy and is denoted by the symbol S.

At equilibrium, Gibbs free energy (ΔG) is _(value)

0

Adding platinum to this reaction will increase the reaction rate because the platinum acts as a _. A catalyst speeds up a chemical reaction by _ but is not _

Adding platinum to this reaction will increase the reaction rate because the platinum acts as a catalyst. A catalyst speeds up a chemical reaction by lowering the activation energy but is not used up in the reaction.

what is the relation between entropy and temperature?

As the temperature of a system increases, the entropy also increases.

Entropy (symbol and definition)

Entropy, denoted by the symbol S, is the thermodynamic property describing the amount of molecular randomness or disorder in a system.

Gibbs free energy change (ΔG) is a thermodynamic property that determines whether a process will_

Gibbs free energy change (ΔG) is a thermodynamic property that determines whether a process will occur spontaneously at constant pressure and temperature

The general thermodynamic formula that is used to predict the spontaneity of a chemical reaction is the _

Gibbs free energy, defined as follows: ΔG∘=ΔH∘−TΔS∘, whereΔG∘ is the standard change in free energy from the reaction, ΔH∘ is the standard change of enthalpy (heat flow) in the reaction, T is the temperature in kelvins, and ΔS∘ is the standard change in entropy (disorder) during the reaction.

what ΔG∘ states a reaction will happen? spontaneous vs nonspontaneous?

If ΔG∘ is negative for a given reaction, it means that there will be a net flow of free energy from the reacting system into the environment, and the reaction is favored thermodynamically. Such a reaction is said to be spontaneous.

The third law of thermodynamics relates the entropy (randomness) of matter to its absolute temperature. Which of the following statements are in agreement with the third law of thermodynamics? (3) At zero degrees kelvin, substances maximize entropy. In a crystalline state, there is a tendency to minimize entropy. At the melting point, the entropy of a system increases abruptly as the compound transforms into a liquid. At absolute zero, the interatomic distance within a crystal is minimized. As the temperature of a perfect crystal increases, the random vibrations of the molecules decrease. In a gaseous state, the entropy of the system is zero.

In a crystalline state, there is a tendency to minimize entropy. At the melting point, the entropy of a system increases abruptly as the compound transforms into a liquid. At absolute zero, the interatomic distance within a crystal is minimized.

what happens in a galvanic cell that results in a voltage?

In a galvanic cell, a spontaneous redox reaction occurs. However, the reactants are separated such that the transfer of electrons is forced to occur across a wire. The resulting electricity is measured in volts (V)

what is meant by saying that entropy is a state thermodynamic function?

It is a state thermodynamic function, meaning that its value does not depend on the path used to arrive at a specific set of conditions.

how catalyst relates to equilibrium constant?

It is important to note that catalysts do not change the thermodynamic properties of a reaction. A catalyst cannot change the equilibrium constant of a reaction.

what does positive vs negative for standard free energy of formation means?

Negative values for a formation reaction indicate thermodynamic stability of the product. In other words, the compound formed does not spontaneously decompose back into the component elements. Positive values for a formation reaction indicate thermodynamic instability of the product.

what values of E∘ and ΔG∘ are needed for a spontaneous reaction?

Since E∘ is positive and ΔG∘ is negative, this reaction is spontaneous under standard conditions.

what is the entropy change? (symbol)

The entropy change, ΔS, is the difference in entropy between two states of a system, such as between the reactants and products of a reaction or between a flask before and after adding a mixture of gas.

why a reaction is slow even if it is thermodynamically favorable? explain

The reason that the above reaction occurs so slowly is that bonds must be broken before anything else can proceed. The bond-breaking event requires a certain amount of energy. This energy barrier is known as the activation energy of the reaction.

how standard free energy of formation can be used?

The sign of ΔG∘f can be used to predict the feasibility of synthesizing a substance from its component elements. T

what is the symbol of standard free energy change for a reaction? how can be calculated?

The standard free energy change for a reaction, ΔG∘, is a state function and can be calculated from the standard free energies of formation as follows: ΔG∘rxn=∑npΔG∘f(products)−∑nrΔG∘f(reactants) where np and nr represent the stoichiometric coefficients in the balanced chemical equation for the reactants and products respectively.

what is the standard free energy of formation?

The standard free energy of formation, ΔG∘f, of a substance is the free energy change for the formation of one mole of the substance from the component elements in their standard states.

What is standard molar entrpy?

The standard molar entropy is the absolute entropy of one molar substance in standard state.

what does standard reduction potential tells about a substance?

The standard reduction potential for a substance indicates how readily that substance gains electrons relative to other substances at standard conditions.

The state functions are independent of_, and depend only on _

The state functions are independent of the path followed by the reaction, and depend only on the difference between the beginning and the final points of the reaction.

The third law of thermodynamics deals with the _of a system and the_ in the molecules. Whenever there is a change in _, the_ of molecules increase; therefore, the entropy of the system - as the phase changes. At absolute zero, the entropy of any perfect system becomes _.

The third law of thermodynamics deals with the entropy of a system and the chemical bonding in the molecules. Whenever there is a change in phase from a solid to a liquid or from a liquid to a gas, the vibrational and rotational motions of molecules increase; therefore, the entropy of the system increases as the phase changes. At absolute zero, the entropy of any perfect system becomes zero.

the standard free energy of formation are applicable under what temperature?

These values are applicable at 25 ∘C and are found in thermodynamic tables.

an increase in temperature affects the _(3)

an increase in temperature affects the physical state, molecular motion, and entropy of a substance.

From this example you can see that thermodynamics can predict whether a reaction is favored, but it says nothing about the rate at which the reaction will occur. To understand rates of reactions, we must turn to _

chemical kinetics.

The more positive the reduction potential, the more _ (in terms of electrons)

easily the substance gains electrons.

Be aware, however, that spontaneous does not mean _

instantaneous, and that thermodynamically favored reactions may still occur very slowly.

Spontaneous processes, such as a solid melting above its melting point, are_ according to the scientific definition

not reversible

E is _

potential

Since E∘ is positive and ΔG∘ is negative, this reaction is _ under standard conditions.

spontaneous

entropy is a _

state function (capital S)

thermodynamics quantifies the _of a system

state functions

The third law of thermodynamics relates _to its_

the entropy (randomness) of matter to its absolute temperature.

The value of ΔG∘f for a substance gives a measure of the _ with respect to the component elements.

thermodynamic stability

The entropy of a pure perfect crystal at 0K is _

zero.

what is the symbol of standard energy of formation?

ΔG∘f

what the positive vs negative values of ΔS mean?

ΔS has a positive value when disorder increases and a negative value when disorder decreases.