Question 1

Which of the following statements about equilibrium is/are true? I.$\Delta$G_sys = 0 II.$\Delta$S_sys = 0 III.$\Delta$S_univ = 0

Accepted Answer

Equilibrium is achieved when the rate of the forward reaction is equal to the rate of the reverse reaction. In order to represent this, the equation: F1F1F1S1F1F1F10G_sys = 0 is used, where F1F1F1S1 represents the reactants, F1F1F10S represents the products, G_sys represents the Gibbs free energy change for the system, and the subscript 0 indicates standard state conditions. Statements I and III, where S_univ and G_sys, respectively, represent equilibrium, so both of those statements are true. Statement II, where there is no Gibbs free energy term, is not a valid representation of equilibrium, so it is false. Therefore, the correct choice is E (both I and III).

Question 2

The enthalpy and entropy of vaporization of ethanol are 38.6 kJ/mol and 109.8 J/mol . K,respectively.What is the normal boiling point of ethanol,in S1U1P1$\circ$S1S1P0C?

Accepted Answer

The normal boiling point of a substance is the temperature at which its vapor pressure is equal to 1 atm. To calculate the normal boiling point of ethanol, we need to use the Clausius-Clapeyron equation:
ln(P2/P1) = (ΔHvap/R)((1/T1) - (1/T2))
where P1 and P2 are the vapor pressures at the two temperatures T1 and T2, ΔHvap is the enthalpy of vaporization, R is the gas constant, and ln is the natural logarithm.
We can assume that the vapor pressure at the normal boiling point is equal to 1 atm, and use the given enthalpy and entropy values to solve for the normal boiling point.
At the normal boiling point:
P1 = 1 atm
P2 = 101325 Pa
ΔHvap = 38.6 kJ/mol = 38600 J/mol
ΔSvap = 109.8 J/mol K
R = 8.314 J/mol K
Substituting these values into the equation and converting temperatures to Kelvin:
ln(101325/1) = (38600/8.314)((1/T1) - (1/373.15))
Simplifying and solving for T1:
T1 = 351.5 K or 78.4°C
Therefore, the normal boiling point of ethanol is 78.4°C or 173.1°F, which corresponds to choice B.

Question 3

Dinitrogen tetroxide (N₂O₄)decomposes to nitrogen dioxide (NO₂).If $\Delta$HS1U1P1$\circ$S1S1P0 = 58.02 kJ/mol and $\Delta$SS1U1P1$\circ$S1S1P0 = 176.1 J/mol . K,at what temperature are reactants and products in their standard states at equilibrium?

Accepted Answer

The equilibrium constant is given by:K = exp(-ΔG°/RT)where ΔG° is the standard free energy change, R is the gas constant, and T is the temperature.We are given that ΔG° = 58.02 kJ/mol and R = 8.314 J/mol K. Substituting these values into the equation, we get:K = exp(-58020 J/mol / (8.314 J/mol K * T))We are also given that the equilibrium constant is 176.1 J/mol K. Substituting this value into the equation, we get:176.1 J/mol K = exp(-58020 J/mol / (8.314 J/mol K * T))Solving for T, we get:T = 56.3 KTherefore, the correct answer is A.

Question 4

At what temperature does the Fe(s)$\leftrightarrows$ Fe(g)phase transition occur? $\Delta$H= 415.5 kJ/mol; $\Delta$S = 153.4 J/mol . K.

Accepted Answer

The answer of At what temperature does the Fe(s)$\leftrightarrows$ Fe(g)phase...

Question 5

The entropy of vaporization of water is 109.0 J/mol . K at its normal boiling point.What is the enthalpy of vaporization of water at this temperature?

Accepted Answer

By definition, the enthalpy of vaporization is the amount of energy required to vaporize one mole of a substance at its normal boiling point. It is related to the entropy of vaporization (ΔSvap) by the equation ΔHvap = TΔSvap. Thus, we can find the enthalpy of vaporization of water at its normal boiling point (100°C, or 373.15 K) using the given entropy of vaporization (109.0 J/mol K) as follows:

ΔHvap = TΔSvap = (373.15 K)(109.0 J/mol K) = 40.66 kJ/mol

Therefore, the answer is D (+40.66 kJ/mol).

Question 6

Which of the following statements regarding coupled reactions and how they sustain life is NOT correct?

Accepted Answer

Production of glucose by plants is not a spontaneous process. It requires energy input from sunlight and the process of photosynthesis to occur. Spontaneous reactions involve a release of energy without requiring an input of energy.

Question 7

The enthalpy of fusion for benzene is 127.34 kJ/kg,and its melting point is 5.49S1U1P1$\circ$S1S1P0C.What is the entropy change when 1 mole of benzene melts at 5.49S1U1P1$\circ$S1S1P0C?

Accepted Answer

The entropy change (ΔS) can be calculated using the formula ΔS = ΔH/T, where ΔH is the enthalpy of fusion and T is the temperature in Kelvin. First, convert the melting point from Celsius to Kelvin (5.49°C + 273.15 = 278.64 K). Then, convert the enthalpy of fusion from kJ/kg to J/mol using the molar mass of benzene (78.11 g/mol). ΔH = 127.34 kJ/kg * 78.11 g/mol * 1000 J/kJ / 1000 g/kg = 9950.5 J/mol. Finally, ΔS = 9950.5 J/mol / 278.64 K = 35.696 J/K.

Question 8

If a reaction A$\to$ B has  ,then when the reaction is at equilibrium there will be __________

Accepted Answer

The answer of If a reaction A$\to$ B has ...

Question 9

The enthalpy of fusion for benzene is 127.34 kJ/kg,and its melting point is 5.49S1U1P1$\circ$S1S1P0C.Estimate $\Delta$GS1U1P1$\circ$S1S1P0 when 1.00 mole of benzene melts at 25.00S1U1P1$\circ$S1S1P0C.

Accepted Answer

The Gibbs free energy change (ΔG) for melting at a temperature different from the melting point can be estimated using ΔG = ΔH - TΔS. Since melting is spontaneous at the melting point, ΔG = 0 at 5.49°C. At 25°C, ΔG can be estimated using the enthalpy of fusion and the temperature difference.

Question 10

Consider the reaction 4 Fe(s)+ 3 O₂(g)$\to$ 2 Fe₂O₃(s),for which $\Delta$HS1U1P1$\circ$S1S1P0 = -1648.4 kJ/mol and $\Delta$SS1U1P1$\circ$S1S1P0 = -549.5 J/mol . K.Which of the following statements regarding its temperature dependence is true?

Accepted Answer

The reaction is exothermic (ΔH° = -1648.4 kJ/mol) and has a negative entropy change (ΔS° = -549.5 J/mol·K). According to Gibbs free energy equation (ΔG° = ΔH° - TΔS°), the reaction is spontaneous at low temperatures where the enthalpy term dominates and nonspontaneous at high temperatures where the negative entropy term becomes significant.

Question 11

The equilibrium vapor pressure for benzene is 94.4 mmHg at 298 K.When liquid benzene is in equilibrium with its vapor,which of the following must apply?

Accepted Answer

When liquid benzene is in equilibrium with its vapor, the system is at constant temperature and pressure. Therefore, the Gibbs free energy change for the process (liquid benzene to vapor) must be zero (F1F1F1S1F1F1F10G = 0).

At equilibrium, the rate of vaporization equals the rate of condensation. Therefore, the vapor pressure of benzene must remain constant. This means that the slope of the equilibrium vapor pressure curve (ln P vs. 1/T) must be zero (F1F1F1S1F1F1F10GF1F1F1S1F1F1F10 > 0).

Question 12

Benzene is a liquid under standard conditions.The standard enthalpy and entropy change for the evaporation of liquid benzene to form benzene vapor are +33.9 kJ/mol and 96.3 J/mol . K,respectively.If liquid benzene is placed in a closed container at 78.85S1U1P1$\circ$S1S1P0C,which of the following statements is true?

Accepted Answer

The standard enthalpy change for the evaporation of liquid benzene is positive, indicating that the process is endothermic and requires energy input. However, the positive entropy change shows that the process is spontaneous and favors the formation of vapor molecules. At a given temperature, there is a dynamic equilibrium between the liquid and vapor phases of a substance, and the equilibrium vapor pressure increases with temperature. At 78.85°C, the vapor pressure of benzene is lower than 1 bar, but the liquid benzene will still evaporate until the vapor pressure reaches equilibrium with the liquid phase, which means that choice B is the best answer. The other options are incorrect because they contradict the principles of thermodynamics and phase equilibrium.

Question 13

Which of the following is/are true for a reversible process at equilibrium? I.$\Delta$S_univ = 0 II.$\Delta$S_sys = 0 III.$\Delta$G_sys = 0

Accepted Answer

For a reversible process at equilibrium, both the system and the surroundings are in a state of constant entropy, which means that ΔSsystem = ΔSsurroundings = 0. Therefore, the first and second equations are true: I. F1F1F1S1F1F1F10S_univ = 0 (where U1B1univ stands for the total internal energy of the universe) II. F1F1F1S1F1F1F10S_sys = 0 (where U1B1sys stands for the internal energy of the system) However, the third equation is not true because the Gibbs free energy change of a reversible process at equilibrium can only be equal to zero if the process occurs at constant temperature and pressure. Therefore, we cannot assume that ΔG = 0 for a reversible process at equilibrium without specifying these conditions.

Question 14

A reaction is at equilibrium at a given temperature and constant pressure when __________

Accepted Answer

At equilibrium, the forward and reverse reactions occur at equal rates, so the net change in the concentrations of reactants and products is zero. This can be expressed mathematically using the equilibrium constant (K), which relates the concentrations of reactants and products at equilibrium. The equation given in choice C correctly represents the equilibrium condition, with the forward reaction written as F1F1F1S1 → F1F1F10G and the reverse reaction written as F1F1F10G → F1F1F1S1. The subscript "rxn" indicates that these are the reactants and products of the overall reaction. The notation "_{" and "}" represents the standard states of the reactants and products, respectively. The equilibrium constant is defined as K = [F1F1F10G] / [F1F1F1S1], and at equilibrium, K = 1.

Question 15

What is the overall standard free energy change for the following two reactions? A + B $\to$ C = $\Delta$G₁ C + D $\to$ E = $\Delta$G₂

Accepted Answer

The answer of What is the overall standard free energy...

Question 16

The enthalpy and entropy of fusion for sodium chloride are 481.9 kJ/kg and 26.22J/mol . K,respectively.At a total pressure of 1 bar,at what temperature can solid and liquid NaCl coexist at equilibrium?

Accepted Answer

The answer of The enthalpy and entropy of fusion for...

Question 17

Consider the reaction HgO(s)+ Zn(s)$\to$ ZnO(s)+ Hg(s),for which $\Delta$HS1U1P1$\circ$S1S1P0 = -259.7 kJ/mol and $\Delta$SS1U1P1$\circ$S1S1P0 = 7.8 J/mol . K.Which of the following statements regarding its temperature dependence is true?

Accepted Answer

The answer of Consider the reaction HgO(s)+ Zn(s)$\to$ ZnO(s)+ Hg(s),for...

Question 18

Consider the freezing of water at -10.0S1U1P1$\circ$S1S1P0C.What are the signs of $\Delta$H_fus,$\Delta$S_fus,and $\Delta$G_fus at this temperature?

Accepted Answer

The answer of Consider the freezing of water at -10.0S1U1P1$\circ$S1S1P0C.What...

Question 19

Which of the following statements regarding glycolysis,glucose phosphorylation,and ATP^4- hydrolysis is NOT correct?

Accepted Answer

Glucose phosphorylation happens spontaneously under physiological conditions, therefore statement B is not correct.

Question 20

In a biochemical reaction,A + B $\to$ C with   = 30 kJ/mol.Which of the following reactions might be effectively coupled to this reaction so that it becomes more spontaneous?
(I)C + D $\to$ B + E 
 = -40 kJ/mol

(II)C + D $\to$ B + E  
 = +40 kJ/mol

Accepted Answer

The answer of In a biochemical reaction,A + B $\to$...

Quiz 12: Thermodynamics-Why Chemical Reactions Happen

Which of the following statements about equilibrium is/are true? I. $\Delta$ G_sys = 0 II. $\Delta$ S_sys = 0 III. $\Delta$ S_univ = 0

The enthalpy and entropy of vaporization of ethanol are 38.6 kJ/mol and 109.8 J/mol . K,respectively.What is the normal boiling point of ethanol,in ^$\circ$C?

Dinitrogen tetroxide (N₂O₄) decomposes to nitrogen dioxide (NO₂) .If $\Delta$ H^$\circ$ = 58.02 kJ/mol and $\Delta$ S^$\circ$ = 176.1 J/mol . K,at what temperature are reactants and products in their standard states at equilibrium?

At what temperature does the Fe(s) $\leftrightarrows$ Fe(g) phase transition occur? $\Delta$ H= 415.5 kJ/mol; $\Delta$ S = 153.4 J/mol . K.

The entropy of vaporization of water is 109.0 J/mol . K at its normal boiling point.What is the enthalpy of vaporization of water at this temperature?

Which of the following statements regarding coupled reactions and how they sustain life is NOT correct?

The enthalpy of fusion for benzene is 127.34 kJ/kg,and its melting point is 5.49^$\circ$C.What is the entropy change when 1 mole of benzene melts at 5.49^$\circ$C?

The enthalpy of fusion for benzene is 127.34 kJ/kg,and its melting point is 5.49^$\circ$C.Estimate $\Delta$ G^$\circ$ when 1.00 mole of benzene melts at 25.00^$\circ$C.

Consider the reaction 4 Fe(s) + 3 O₂(g) $\to$ 2 Fe₂O₃(s) ,for which $\Delta$ H^$\circ$ = -1648.4 kJ/mol and $\Delta$ S^$\circ$ = -549.5 J/mol . K.Which of the following statements regarding its temperature dependence is true?

The equilibrium vapor pressure for benzene is 94.4 mmHg at 298 K.When liquid benzene is in equilibrium with its vapor,which of the following must apply?

Which of the following is/are true for a reversible process at equilibrium? I. $\Delta$ S_univ = 0 II. $\Delta$ S_sys = 0 III. $\Delta$ G_sys = 0

A reaction is at equilibrium at a given temperature and constant pressure when __________

The enthalpy and entropy of fusion for sodium chloride are 481.9 kJ/kg and 26.22J/mol . K,respectively.At a total pressure of 1 bar,at what temperature can solid and liquid NaCl coexist at equilibrium?

Consider the reaction HgO(s) + Zn(s) $\to$ ZnO(s) + Hg(s) ,for which $\Delta$ H^$\circ$ = -259.7 kJ/mol and $\Delta$ S^$\circ$ = 7.8 J/mol . K.Which of the following statements regarding its temperature dependence is true?

Consider the freezing of water at -10.0^$\circ$C.What are the signs of $\Delta$ H_fus, $\Delta$ S_fus,and $\Delta$ G_fus at this temperature?

Which of the following statements regarding glycolysis,glucose phosphorylation,and ATP^4- hydrolysis is NOT correct?

Quiz 12: Thermodynamics-Why Chemical Reactions Happen

Which of the following statements about equilibrium is/are true? I. Δ\DeltaΔ Gsys = 0 II. Δ\DeltaΔ Ssys = 0 III. Δ\DeltaΔ Suniv = 0

The enthalpy and entropy of vaporization of ethanol are 38.6 kJ/mol and 109.8 J/mol . K,respectively.What is the normal boiling point of ethanol,in ∘\circ∘ C?

Dinitrogen tetroxide (N2O4) decomposes to nitrogen dioxide (NO2) .If Δ\DeltaΔ H ∘\circ∘ = 58.02 kJ/mol and Δ\DeltaΔ S ∘\circ∘ = 176.1 J/mol . K,at what temperature are reactants and products in their standard states at equilibrium?

At what temperature does the Fe(s) ⇆\leftrightarrows⇆ Fe(g) phase transition occur? Δ\DeltaΔ H = 415.5 kJ/mol; Δ\DeltaΔ S = 153.4 J/mol . K.

The entropy of vaporization of water is 109.0 J/mol . K at its normal boiling point.What is the enthalpy of vaporization of water at this temperature?

Which of the following statements regarding coupled reactions and how they sustain life is NOT correct?

The enthalpy of fusion for benzene is 127.34 kJ/kg,and its melting point is 5.49 ∘\circ∘ C.What is the entropy change when 1 mole of benzene melts at 5.49 ∘\circ∘ C?

If a reaction A →\to→ B has ,then when the reaction is at equilibrium there will be __________

The enthalpy of fusion for benzene is 127.34 kJ/kg,and its melting point is 5.49 ∘\circ∘ C.Estimate Δ\DeltaΔ G ∘\circ∘ when 1.00 mole of benzene melts at 25.00 ∘\circ∘ C.

Consider the reaction 4 Fe(s) + 3 O2(g) →\to→ 2 Fe2O3(s) ,for which Δ\DeltaΔ H ∘\circ∘ = -1648.4 kJ/mol and Δ\DeltaΔ S ∘\circ∘ = -549.5 J/mol . K.Which of the following statements regarding its temperature dependence is true?

The equilibrium vapor pressure for benzene is 94.4 mmHg at 298 K.When liquid benzene is in equilibrium with its vapor,which of the following must apply?

Which of the following is/are true for a reversible process at equilibrium? I. Δ\DeltaΔ Suniv = 0 II. Δ\DeltaΔ Ssys = 0 III. Δ\DeltaΔ Gsys = 0

A reaction is at equilibrium at a given temperature and constant pressure when __________

What is the overall standard free energy change for the following two reactions? A + B →\to→ C = Δ\DeltaΔ G1 C + D →\to→ E = Δ\DeltaΔ G2

The enthalpy and entropy of fusion for sodium chloride are 481.9 kJ/kg and 26.22J/mol . K,respectively.At a total pressure of 1 bar,at what temperature can solid and liquid NaCl coexist at equilibrium?

Consider the reaction HgO(s) + Zn(s) →\to→ ZnO(s) + Hg(s) ,for which Δ\DeltaΔ H ∘\circ∘ = -259.7 kJ/mol and Δ\DeltaΔ S ∘\circ∘ = 7.8 J/mol . K.Which of the following statements regarding its temperature dependence is true?

Consider the freezing of water at -10.0 ∘\circ∘ C.What are the signs of Δ\DeltaΔ Hfus, Δ\DeltaΔ Sfus,and Δ\DeltaΔ Gfus at this temperature?

Which of the following statements regarding glycolysis,glucose phosphorylation,and ATP4- hydrolysis is NOT correct?

In a biochemical reaction,A + B →\to→ C with = 30 kJ/mol.Which of the following reactions might be effectively coupled to this reaction so that it becomes more spontaneous? (I) C + D →\to→ B + E = -40 kJ/mol (II) C + D →\to→ B + E = +40 kJ/mol

Which of the following statements about equilibrium is/are true? I. $\Delta$ G_sys = 0 II. $\Delta$ S_sys = 0 III. $\Delta$ S_univ = 0

The enthalpy and entropy of vaporization of ethanol are 38.6 kJ/mol and 109.8 J/mol . K,respectively.What is the normal boiling point of ethanol,in ^$\circ$C?

Dinitrogen tetroxide (N₂O₄) decomposes to nitrogen dioxide (NO₂) .If $\Delta$ H^$\circ$ = 58.02 kJ/mol and $\Delta$ S^$\circ$ = 176.1 J/mol . K,at what temperature are reactants and products in their standard states at equilibrium?

At what temperature does the Fe(s) $\leftrightarrows$ Fe(g) phase transition occur? $\Delta$ H= 415.5 kJ/mol; $\Delta$ S = 153.4 J/mol . K.

The enthalpy of fusion for benzene is 127.34 kJ/kg,and its melting point is 5.49^$\circ$C.What is the entropy change when 1 mole of benzene melts at 5.49^$\circ$C?

The enthalpy of fusion for benzene is 127.34 kJ/kg,and its melting point is 5.49^$\circ$C.Estimate $\Delta$ G^$\circ$ when 1.00 mole of benzene melts at 25.00^$\circ$C.

Consider the reaction 4 Fe(s) + 3 O₂(g) $\to$ 2 Fe₂O₃(s) ,for which $\Delta$ H^$\circ$ = -1648.4 kJ/mol and $\Delta$ S^$\circ$ = -549.5 J/mol . K.Which of the following statements regarding its temperature dependence is true?

Which of the following is/are true for a reversible process at equilibrium? I. $\Delta$ S_univ = 0 II. $\Delta$ S_sys = 0 III. $\Delta$ G_sys = 0

Consider the reaction HgO(s) + Zn(s) $\to$ ZnO(s) + Hg(s) ,for which $\Delta$ H^$\circ$ = -259.7 kJ/mol and $\Delta$ S^$\circ$ = 7.8 J/mol . K.Which of the following statements regarding its temperature dependence is true?

Consider the freezing of water at -10.0^$\circ$C.What are the signs of $\Delta$ H_fus, $\Delta$ S_fus,and $\Delta$ G_fus at this temperature?

Which of the following statements regarding glycolysis,glucose phosphorylation,and ATP^4- hydrolysis is NOT correct?