Exam 18: Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

Carbon atoms can be found in a variety of elemental forms. At sufficiently high temperature, carbon is an atomic gas. At room temperature, both tetrahedral networks in diamond and trigonal planar networks in graphite can be found. Trigonal planar networks of carbon atoms are also found in Buckminsterfullerene (C₆₀). How does the standard entropy of these forms vary per mole of carbon?

In an experiment, 1.00 atm of H₂(g) in a 10.0 L container at 25°C was reacted under standard state conditions with a stoichiometric quantity of O₂(g) to form water vapor: H₂(g) + $\frac { 1 } { 2 }$ O₂(g) $\rightarrow$ H₂O(g). What is the entropy change for the reaction? Substance (/\cdot) (g) 130.58 (g) 205.0 (g) 188.83

Considering the tabulated values for the thermodynamic properties of oxygen gas, why is the standard entropy nonzero but the standard enthalpy and free energy of formation are zero?

What is the entropy change if 4.500 g of CaCO₃(s) is placed in a container and allowed to decompose to CaO(s) and CO₂(g) according to the following reaction? CaCO₃(s) $\leftrightarrow$ CaO(s) + CO₂(g) Substance (/\cdot) (s) 92.88 (s) 39.75 (g) 213.6

The entropy of an oxygen molecule in air corresponds to approximately 1 * 10¹⁰ accessible states. Which of the following states contribute most to this entropy? I.translational II. rotational III. vibrational IV. electronic

A qualitative interpretation of the effect of temperature on equilibrium views heat as a reactant or product and explains shifts in equilibrium with temperature as responses to stress to the equilibrium. How does van 't Hoff's equation refine this view?

Determine $\Delta$ S ^°rxn for N₂O₄(g) $\leftrightarrow$ 2NO₂(g) given the following information: Substance (/\cdot) (g) 304.3 (g) 240.45

The standard entropy of diamond is 2.4 J/mol . K. Calculate the entropy per carbon atom in diamond and the number of microstates for each atom. Discuss the number of microstates in terms of the molecular motions accessible to each carbon atom.

What is the standard entropy change when 10.0 g of methane reacts with 10.0 g of oxygen? CH₄(g) + 2O₂(g) $\rightarrow$ CO₂(g) + 2H₂O(l) Substance (/\cdot) (g) 186.2 (g) 205.0 (l) 70.0 (g) 213.6

Indicate which one of the following reactions most certainly results in a negative $\Delta$ S_sys.

For a particular hypothetical reaction, 2A + B $\rightarrow$ C, the value of $\Delta$ G $\degree$ is 250 kJ/mol. What is the value of $\Delta$ G for this reaction at 298 K when [A] = 0.60 M, [B] = 0.10 M, and [C] = 4.0 * 10^-3 M?

The reaction Cr(NH₃)₆³⁺(aq) + 3 en(aq) $\leftrightarrow$ Cr(en)₃³⁺(aq) + 6 NH₃(aq) Where en represents ethylenediamine, has a small value for the enthalpy change, $\Delta$ _rxn, yet the equilibrium constant for this reaction is large because ________

What is the difference between $\Delta$ G and $\Delta$ G $\degree$ ?

The following figures represent distributions of gas molecules between two containers connected by an open tube. In which figure is the entropy of the system maximized?

Indicate which of the following has the highest entropy at 298 K.

If for a given chemical reaction at 298 K, both the change in free energy, $\Delta$ G, and the change in the standard free energy, $\Delta$ G°, are positive with $\Delta$ G > $\Delta$ G°, then ________

Hydrogen iodide can theoretically be made by the reaction of hydrogen gas and iodine by the following reaction: H₂(g) + I₂(s) $\rightarrow$ 2HI(g) What temperature conditions are required for the formation of HI to be favored at standard pressure? S°(H₂, g) = 130.6 J/(mol .K) S°(I₂, s) = 116.1 J/(mol . K) S°(HI, g) = 206.6 J/(mol . K) $\Delta$ $H _ { f } ^ { \circ }$ (HI, g) = 26.5 kJ/mol