Exam 3 Energetics Flashcards
Is it energetically favorable for ice to melt at 263 K (-10 ˚C), where ΔH is +5630 J/mol and ΔS is +20.6 J/K•mol?
ΔG is positive and the melting of ice at 263 K is unfavorable.
True or False? The entropy of an open system can decrease.
True
An organism takes in nutrients, often in the form of high-entropy small molecules, and from them it builds enormous, complex, highly ordered macromolecules like proteins and nucleic acids, which constructs elegantly structured cells, tissues, and organs. This is an example of what?
Entropy decreasing in an open system.
In order for the entropy of an open system to decrease, it requires what?
An accompanying large decrease in enthalpy.
True or False?
Living organisms spend energy to overcome entropy.
True
True or False?
For these life processes to occur, the overall free energy changes in the organism must be positive; thus, life is an irreversible process
False
What does it mean when an organism comes to equilibrium with its surroundings.
That organism is dead.
True or False?
The portion of an energy change in process that is available, or free, to do useful work at constant T, P is the definition of Delta G.
True
True or False?
The sign of ∆H for a process tells us whether that process, or its reverse, is thermodynamically favorable.
False it is ∆G
True or False?
The magnitude of ∆G is an indication of how far the process is from equilibrium and how much useful work may be obtained from it.
True
True or False?
A thermodynamically favored process tends in the direction that maximizes free energy because it results in a negative ∆G.
False. minimizing ∆G would cause it to be negative which is favored.
True or False?
Since free energy is a state function, free energy change for any reaction will equal the free energy of the products minus that of the reactants.
True
True or False?
For a reaction that is exergonic, ΔG = 0 because there is no driving force in either direction.
False. ΔG = 0 at equilibrium
True or False?
The metabolic processes can occur only when each has a favorable thermodynamic driving force, that is, when ∆G < 0, within relatively narrow ranges of temperature, pH, and concentrations for ions and metabolites.
True
True or False?
The concentrations of certain solutes inside cells remain relatively constant.
True
True or False?
In the steady state, continuous free energy is put into the system to maintain homeostasis.
True
Thermodynamic definition of entropy change at constant pressure is __________.
_______represents the heat transferred from the system to the surroundings at constant pressure and some temperature T.
∆Hsystem
True or False?
The negative sign represents a loss of energy by the system and a gain of energy by the surroundings.
True
True or False?
Free energy is not relevant to bioenergetics because most cells and organisms live under conditions of constant pressure and temperature.
False. it is relevant
Define Delta G
The amount of ‘free’ energy in a system to do useful work under the given conditions, specifically constant temperature
What is the formula for free energy?
What is the formula for The free energy of solute?
For a typical favorable process ∆G must be what?
∆G must be negative, i.e. ∆G < 0
True or false?
A decrease in energy (∆H < 0) and/or an increase in entropy (∆S > 0), makes ∆G positive.
False
If Delta G is zero, then the free energy is _____, meaning the process is at _____.
Delta G at zero means the free energy is zero and the process is in equilibrium.
True or False?
If delta G is positive then free energy is required to do work and the process is thermodynamically unfavorable, but so is the reverse process.
False. the process is thermodynamically unfavorable, but the reverse is favorable.
If Delta G is negative then free energy is __________ and the process is thermodynamically ___________.
If delta G is negative then there is free energy available to do work and the process is thermodynamically favorable.
If delta G is negative then there is free energy available to do work so the process is then ____________.
Exergonic. (spontanteous)
Is it energetically favorable for ice to melt at 283 K (+10 ˚C), where ΔH is +6770 J/mol and ΔS is +24.7 J/K•mol?
ΔG is negative and the melting of ice at at 283 K is favorable.
At the melting temperature of water, 273 K (0 ℃), ∆H and T∆S terms are both equal to __________ and ∆G equals _______.
∆H and T∆S terms are both equal to each other @ 6010 J/mol and ∆G equals 0.
At the melting temperature of water, ∆H and T∆S terms are both equal and ∆G is zero because ____________.
Ice and liquid water are in equilibrium at 273 K
Can melt a bit more ice by adding a minute amount of heat
Can freeze a bit more water by taking a minute amount of heat away
True or False?
The melting point of any substance is the temperature at which the values for ∆H and T∆S are equal.
True
True or False?
At the melting temperature of water, both ∆H or ∆S alone can tell us what will happen and which form or water is stable at any temperature.
False. Neither ∆H nor ∆S alone can tell us what will happen. It is their combination, expressed as ∆H - T∆S, that defines exactly which form of water is stable at any temperature.
Explain the picture below.
In the fermentation of glucose to ethanol
Explain the picture below
Explain the picture below
Delta H represents the sum of the heats of formation, commonly measured in kJ/mol, of the products minus the sum of those of the reactants. This called ___________
Enthalpy
Entropy is a measurement of randomness or disorder. It is represented by the symbol___.
Delta S
The effect of temperature on delta G for a process depends on the signs of ____ and _____.
Delta S and Delta H
If Delta H is positive and Delta S is positive at low temperature then _________.
Delta G is positive and not favored
If Delta H is positive and Delta S is negative at any temperature then _________.
Delta G is positive and not favored
If Delta H is negative and Delta S is positive at any temperature then _________.
Delta G is negative and therefore favored
If Delta H is positive and Delta S is positive at high temperature then _________.
Delta G is negative and therefore favored
If Delta H and Delta S are both favored at low temperature then Delta G is _________. But if this is the case at a high temperature, then Delta G is ________
Delta G is negative and therefore favored; is positive and therefore unfavored.
True or false?
Favorable processes are rapid processes.
False. The thermodynamic favorability of a process does not determine its rate.
Why does the thermodynamic favorability of a process not determine its rate?
Because a reaction may have a large negative free energy change but still proceed at a slow rate. A good example is a diamond eventually becoming graphite.
True or False?
A diamond is extremely hard because the carbon atoms are strongly bonded in only one direction.
False. The carbon atoms are strongly bonded in all directions.
The carbon atoms of graphite are arranged in planar sheets that can easily glide against each other. This makes it structure _____.
Very soft.
True or False?
Though the thermodynamic favorability of a process does not determine its rate, a catalyst may increase the rate for some reactions and influence the favored direction.
False.
A catalyst increases the rate for some reactions, but the favored direction is always dictated by ∆G and is independent of whether or not the reaction is catalyzed.
True or False?
Enzymes selectively increase the rates for specific, thermodynamically favorable reactions in cells
True
True or False?
The entropy of an open system cannot decrease
False
True or False?
The entropy of an open system can decrease only if this change is accompanied by a small enthalpy decrease
False. this change can only occur if it is accompanied by a large enthalpy decrease because Energy must be expended to pay the price of organization
How do living organisms overcome entropy?
By spending energy
The magnitude of ∆G is an indication of what?
The magnitude of ∆G is an indication of how far the process is from equilibrium and how much useful work may be obtained from it
True or False?
Q, symbolizes the mass action expression for a system that is at equilibrium
False. Q, symbolizes the mass action expression for a system that is not at equilibrium
True or False?
the free energy of any component of the system increases from its standard value with a logarithmic dependence on its activity which is valued by the molar concentration of the solute A.
True The free energy of solute A is expressed by the following equation.
GoA : the standard free energy for solute A at chemical standard state*
(pressure =1 bar, T = 25 ℃ (298.15 K), and solutes at concentrations of 1 M each)
R: the gas constant
T: temperature in units of kelvin
True or False?
Standard state is a precisely defined reference state which can be used to compare thermodynamic properties
True
Since free energy is a state function, free energy change for any reaction will equal the _______ minus that of the _______.
the free energy of the products minus that of the reactants
True or false?
For a reaction at equilibrium, ΔG = 0 because there is no driving force in either direction.
True.
True or False?
This reaction is at equilibrium when G6P and F6P are both at 1 M because ∆G°is positive. Therefore, the equilibrium must lie to the right, with a higher concentration of F6P than G6P
False.
This reaction is Not at equilibrium when G6P and F6P are both at 1 M because ∆G°is positive. This is an endergonic reaction and so reverse reaction is favored under standard conditions. Therefore, the equilibrium must lie to the left, with a higher concentration of G6P than F6P
True or False?
The metabolic processes can occur only when each has a favorable thermodynamic driving force, that is, when ∆G < 0, within relatively narrow ranges of temperature, pH, and concentrations for ions and metabolites.
True
True or False?
In a steady state ∆G > 0. Over time, the system is maintained in a higher state of order than its surroundings
False. ∆G is less than 0, negative.
True or False?
In an equilibrium state, over time, any difference in entropy (state of disorder) between the system and the external environment tends to disappear.
True
What are the conditions of a steady state?
- Constant state requires continual work
- Free energy is continuously put into the system to maintain homeostasis.
- Over time, the system is maintained in a higher state of order than its surroundings
True or False?
In an equilibrium state, net free energy enters and escapes the system.
False.
Net free energy neither enters nor escapes the system
Ionic compounds are maintained at constant concentrations in cells, but only through continually moving ions across the cell membrane. What is this an example of ?
Steady - state
True or false?
Steady-State = Dynamic Equilibrium where all reactions in the body are interrelated, and the system as a whole is in a steady-state condition rather than equilibrium.
True.
Give another example of steady-state in dynamic equilibrium other than ionic compounds.
The sodium-potassium pump. It uses active transport to move molecules from a high concentration to a low concentration.
True or False?
Simple diffusion is an example of steady-state in dynamic equilibrium.
True. Diffusion means the movement of particles from an area of high concentration to an area of low concentration. Dynamic means that things continue to happen - the particles don’t stop moving!
The reverse of this is Equilibrium which means that a balanced situation has been achieved (particles are evenly spread out).
True or False?
Thermoregulation is an example of steady-state in dynamic equilibrium.
True.
With thermoregulation entropy is low internally but high externally and it is an active process that requires energy to keep your internal temperature constant regardless of external affects.
How does a thermodynamically unfavorable reaction become favorable?
By the coupling of unfavorable and favorable reactions
How does coupling make a thermodynamically unfavorable reaction become favorable?
True or False?
Living systems couple favorable and unfavorable processes to drive the unfavorable process forward.
True.
Coupling of this kind is used to drive unfavorable chemical reactions, pump metabolites across membranes against a concentration gradient, transmit nerve impulses, contract muscles, etc.
List and define the 3 types of thermodynamic systems.
Open systems - Can exchange matter and energy with surroundings.
Closed systems - Can exchange energy (e.g. heat or work) but not matter with surroundings.
Isolated systems - Can exchange neither matter nor energy with surroundings
True or False?
Surroundings are anything defined as part of the system.
False
True or False?
Living systems are closed systems.
False.
Living systems are open systems because they can exchange both energy (e.g., heat) and material (e.g., nutrients and excreted wastes) with their environments.
True or False?
A system must have defined boundaries.
True.
Define a system.
Any part of the universe that we choose to study
(i.e., a cell, a Petri dish containing nutrients and millions of cells, the whole laboratory in which this dish rests, or the entire Earth)
The 1st law of thermodynamics states that ___________.
Although energy can be transferred between the system and the surroundings in different ways (i.e., in the form of heat or work), in the chemical processes, energy can be neither created nor destroyed.
True or False?
In an Isolated system, Total energy is constant.
True
True or False?
In a Closed or Open systems, Energy is not conserved
False
As the system loses energy by doing some work on its surroundings, an equal amount of energy must be absorbed by the surroundings. This is due to what?
The 1st law of thermodynamics, energy can neither be created nor destroyed.
True or False?
Energy can be converted from one form to another
True
In EXOTHERMIC reaction, HEAT is a ___ while in a ENDOTHERMIC reaction, HEAT A _______
EXOTHERMIC = HEAT AS PRODUCT
ENDOTHERMIC = HEAT AS REACTANT
This is what type of reaction?
Exothermic Reaction
The system releases energy to the surrounding in the form of heat.
A Catalyst works by_____.
Reducing the activation energy of a reaction.
True or False?
the Enthalpy, ∆H is defined as A measure of the total energy of a thermodynamic system.
True
define Enthalpy.
The heat exchanged between the system and the surroundings at constant pressure (which is the typical condition of living systems).
- The negative sign indicates that the reaction releases energy
True or False?
The energy within a system increases as the energy is transferred as heat to the surroundings.
False. Energy within the system decreases because heat is escaping.
True or False?
A State function Depends only on the initial and final states of the system it describes and is Independent of the pathway taken to get from the initial to the final state.
True
When we place an ice cube in a glass of water at room temperature, it melts. Why doesn’t the rest of the water freeze instead?
Because in fact, all the water has not reached the freezing point at the same time (due to water’s high heat of vapporation). Even a microscopic fraction of a degree above freezing keeps the water from freezing, so until the water reaches a temperature slightly below the freezing point, it remains liquid.
When we touch a flame to a piece of paper, the paper burns to carbon dioxide and water. Why can’t we mix carbon dioxide and water to form paper?
Because heat is what causes CO2 to form but CO2 is not a component of paper.
What is the thermodynamically favored direction for a process?
Thermodynamically favored processes or reactions are those that involve both a decrease in the internal energy of the components (ΔH° < 0) and an increase in entropy of the components (ΔS° > 0). These processes are necessarily “thermodynamically favored” (ΔG° < 0) or negative.
A process is at equilibrium when:
- It is the lowest energy state of the system
- The forward and reverse rates of the process are equal
True or False?
Irreversible processes are set up far from an equilibrium state, and then proceed away from that state
False
Irreversible processes are set up far from an equilibrium state, but then proceed towards the euilibrium state.
True or False?
Thermodynamics does not indicate in which direction a process is favorable
False. Thermodynamics does indicate in which direction a process is favorable. That is the whole purpose of thermodynamics.
True or False?
Irreversible process are often called “spontaneous”, or favorable.
True
Why do chemical and physical processes have thermodynamically favored directions?
Because a Systems natural inclination is to go toward the lowest-energy state by releasing energy as heat
True or False?
Systems have a natural tendency to become less ordered (the increase in entropy, S).
True.
True or False?
Diffusion as an entropy-driven process that although there is practically no energy change, in terms of heat and work, the process is unfavorable.
False. Diffusion is a favorable process despite no energy change.
True or False?
The opposite process of diffusion never occurs.
True. This is why diffusion is a favored process despite no energy change.
The 2nd law of thermodynamics states that ______.
The entropy of an isolated system will tend to increase to a maximum value because Systems have a natural tendency to become less ordered (entropy, S).
True or False?
For a favorable process in an open system, such as a living cell, ∆Suniverse must increase.
True. This is due to the 2nd law of thermodynamics: Systems have a natural tendency to become less ordered.
∆Suniverse = ∆Ssystem + ∆Ssurroundings > 0
True or False?
The 2nd law of thermodynamics states that in all processes involving energy changes under a given set of conditions of temperature and pressure, some energy is dissipated unproductively
True
Give 3 examples of high entropy
Give 3 examples of low entropy
True or false?
Entropy is available for performing work.
False.
Entropy is NOT available for performing work becaue it is the energy that is dissipated unproductively during energy changes.
True of False?
Energy transformations lead to an increase in entropy in a system
True
True or False?
True
Ice and water are at equilibrium at what temperature?
273K
Define the steady-state.
Steady state refers to the maintenance of constant internal concentrations of molecules and ions in the cells and organs of living systems.
- A dynamic steady state = internal composition at both cellular and gross levels are relatively constant, but different from equilibrium concentrations.
- Continuous flux of mass and energy results in the constant synthesis and breakdown of molecules via chemical reactions.
- Steady state can be thought of as homeostasis at a cellular level.
A system with __________ and __________ will never be spontaneous.
positive enthalpy . . . negative entropy
- a positive enthalpy in combination with a negative entropy will always result in a positive value for Gibb’s free energy.
ΔG=(+)−T(−)=+
This means these are the conditions that will always result in a nonspontaneous reaction.
True or False?
An equilibrium constant greater than one would indicate that the equilibrium concentration of products is greater than the equilibrium concentration of reactants, consistent with a spontaneous reaction.
True
If the reaction quotient (Q) is less than the equilibrium constant (K), what is true about the Gibbs free energy?
It is less than zero.
If Q is less than K, then the reaction has not yet reached the equilibrium state. It will proceed spontaneously in the forward direction. Since it is proceeding spontaneously in the forward direction, this must mean that the ΔG (Gibbs free energy) must be negative, or less than zero.
Of the following reactions, which of the following is only spontaneous at high enough temperatures?
a) ∆H –, ∆S + b) ∆H +, ∆S – c) ∆H –, ∆S – d) ∆H +, ∆S +
d) ∆H +, ∆S +
If a reaction has a positive value for its enthalpy and a negative value for its entropy, which of the following is true?
The reaction is at equilibrium
The reaction is spontaneous
Not enough information to tell
The reaction is nonspontaneous
The reaction is nonspontaneous.
- Given the equation for free energy, (delta)G = (delta)H-T(delta)S, we can determine that the reaction is nonspontaneous at all temperatures if H is positive and S is negative. This combination would always lead to a positive G value, meaning that free energy is required for the reaction to take place and it is therefore nonspontaneous.
What must be true of a spontaneous process?
ΔG must be less than 0 and K must be greater than Q
- Change in free energy must always be negative for a spontaneous process. Additionally, Q must be less than K so that the reaction will proceed in the forward reaction, toward equilibrium.
Na(s) + 1/2 Cl2(g) → NaCl (s)
The Standard Heat of formation for NaCl is -411.1 kJ
Which of the following descriptions accurately describes the reaction above?
It is favorable and driven by change in enthalpy only.
Here we are told that the reaction has a favorable enthalpy change (- means energy is released). Qualitatively we can see that the reaction will have an unfavorable change in entropy because the product, being a solid, is more ordered than the reactants which are both solid and gaseous. Thus we can conclude that the reaction is favorable because of the favorable change in enthalpy, which helps to overcome the unfavorable change in entropy.
Calcium carbonate is formed from calcium oxide and carbon dioxide.
CaO(s)+CO2(g)→CaCO3(s)
Given that this reaction is spontaneous at low temperatures and non-spontaneous at high temperatures, what must be true about the change of enthalpy (ΔH) and the change of entropy (ΔS)?
ΔH is less than 0 and ΔS is also less than 0.
- For this particular reaction, ΔS is negative because the total number of moles of gas decreases from reactants to products. Since the reaction is spontaneous at lower temperatures, then ΔG must be negative when T is small. Since the -TΔS term would be positive for all values of T, the only way ΔG can be negative is if ΔH is negative. At higher temperatures, the positve -TΔS term would outweigh the negative ΔH term, resulting in a positive ΔG and a non-spontaneous reaction.
Which of the processes A–D will lead to a positive change in the entropy of the system? If all of these processes lead to a positive change in the entropy of the system, select E.
a. Sodium chloride crystals form as saltwater evaporates.
b. Helium gas escapes from the hole in a balloon.
c. Stalactites form in a cave.
d. Water freezes in a freezer.
e. All of these lead to a positive change in entropy of the system, as they are all spontaneous.
b. Helium gas escapes from the hole in a balloon.
* positive change in the entropy of the system means what leads to more disorder.
Which of the following processes will lead to a decrease in the entropy of the system?
a. Salt crystals dissolve in water.
b. Air escapes from a hole in a balloon.
c. Iron and oxygen react to form rust.
d. Ice melts in your hand.
e. None of these lead to a negative change in the entropy of the system, as they are all spontaneous.
c. Iron and oxygen react to form rust.
* Decrease in entropy = less disorder
Indicate which one of the following reactions results in a negative ΔSsys.
a. H2O(g) ⇔ H2O(s)
b. CaCO3(s) ⇔ CaO(s) + CO2(g)
c. CuSO4(H2O)5 (s) ⇔ CuSO4(s) + 5H2O(g)
d. 14O2(g) + 3NH4NO3(s) + C10H22(l) → 3N2(g) + 17H2O(g) + 10CO2(g)
e. CO2(aq) ⇔ CO2(g)
Any side with more gas has more entropy.
a. H2O(g) ⇔ H2O(s)
Indicate which one of the following reactions result in a positive ΔSsys.
a. AgNO3(aq) + NaCl(aq) ⇔ AgCl(s) + NaNO3(aq)
b. H2O (g) + CO2 (g) ⇔ H2CO3 (aq)
c. H2(g) + I2(g) D 2 Hl(g)
d. C2H2O2(g) ⇔ 2 CO(g) + H2(g)
e. H2O(g) ⇔ H2O(l)
d. C2H2O2(g) ⇔ 2 CO(g) + H2(g)
Because of the ranking for posite Delta S of a system
1. GAS > Liquid > Solid - gas wins over any other
- Molecular Size
- Number of Molecules
4. Dissolved > undissolved
- Temperature
D is correct because of 1 and 4.
Which of the following will have the greatest standard molar entropy (S°)?
a. NH3(g)
b. He(g)
c. C(s, graphite)
d. H2O(l)
e. CaCO3(s)
a. NH3(g)
Because is a gas and has more moles of gas than He
Indicate which of the following has the highest entropy at 298 K.
a. 0.5 g of HCN
b. 1 mol of HCN
c. 2 kg of HCN
d. 2 mol of HCN
e. All of the above have the same entropy at 298 K.
c. 2 kg of HCN
because total grams per mol is 27 and there are 1000 moles in 1 kg. so 2 kg of HCN = 54,000 moles of HCN.
a. 0.5 g of HCN = 1 grams HCN is equal to 0.03700230968417 mole.
b. 1 mol of HCN = 27 grams
d. 2 mol of HCN = 54 grams
In a spontaneous process, which of the following always increases?
a. the entropy of the system
b. the entropy of the surroundings
c. the entropy of the universe
d. the entropy of the system and the universe
e. the entropy of the system, surroundings and the universe
c. the entropy of the universe
ΔSuniverse depends on both ΔSsystem and ΔSsurroundings. ΔSsystem is reflected by ΔSº, (system entropy) while ΔSsurroundings is reflected by ΔHsystem (system enthlpy)
The dissolution of ammonium nitrate in water is a spontaneous endothermic process. It is spontaneous because the system undergoes __________.
b. an increase in entropy.
- If you know it’s spontaneous, then either entropy or enthalpy (or both) must be favorable. If you know one is NOT favorable, then the other must certainly be favorable.
- An endothermic process means that the enthalpy, delta H, isn’t favorable so delta H must have a positive value. For this reaction to be spontaneous and therefore favored as it states, Delta S, entropy, would have to be largely positive, i.e. increase in entropy.
- This change in entropy is large enough that the mathematical product of the temperature (which must be very high) and change in entropy in the Gibbs free energy equation is larger than the change in enthalpy. Therefore, the Gibbs free energy is negative, and the reaction is spontaneous.
Which of the following must be true for a spontaneous exothermic process?
a. only that ΔSsys < 0
b. only that ΔSsys > 0
c. both ΔSsys < 0 and the magnitude of ΔSsys < the magnitude of ΔSsurr
d. both ΔSsys < 0 and the magnitude of ΔSsys > the magnitude of ΔSsurr
e. either ΔSsys > 0, or else ΔSsys < 0 but the magnitude of ΔSsys < the magnitude of ΔSsurr
e. either ΔSsys > 0, or else ΔSsys < 0 but the magnitude of ΔSsys < the magnitude of ΔSsurr
Since Enthalpy is favorable (exothermic), then entropy could be either favorable or unfavorable. But if it’s unfavorable, it must not be bad enough to win over the good enthalpy.
A spontaneous, exothermic process means enthlaphy is favored.
Suppose a chemical reaction is found to be spontaneous, but with ΔSsys < 0. What must be TRUE of the reaction?
ΔSsurr > 0 and the magnitude is ΔSsurr > ΔSsys. In other words, the system loses entropy but the surroundings gain entropy, and the gain by the surroundings outweighs the loss by the system.
- ΔSsys < 0 means that the entropy is not favored
Which of the following statements about equilibrium are true?
I. ΔGsys = 0
II. ΔSsys = 0
III. ΔSuniverse = 0
I. ΔGsys = 0
III. ΔSuniverse = 0
A reaction with a low enthalpy of reaction value is not spontaneous at low temperature but becomes spontaneous at high temperature. What are the signs for ΔH° and ΔS°, respectively?
Both are positive.
This is because “low enthlapy” = delta H is positive;
“Not spontaneous at low temperature but becomes spontaneous at high temperature” = delta S is positive (# 1 and #2a)
1. Entropy factor increases at higher temp
- A temperature “flip” means entropy and enthalpy disagree.
a. If so, high Temp = entropy control,
b. low temp = enthalpy control.
When entropy is favorable, (positive), enthalpy must be______.
Unfavorable (positive)
True or False?
Delta G decreases with increasing Delta H (bond energy) and with increasing entropy.
False. Delta G INCREASES with increasing Delta H and DECREASES with increasing entropy.
True or False?
Spontaneous reactions occur with energy to spare.
True.
