Gen Chem 2 Chapter 18 Guided Reading

Which of the substances below will have the greatest standard molar entropy? C4H10(g) C4H10(l) Kr(g)

C4H10(g) because of its molecular complexity and because gases have translational, rotational, and vibrational modes, allowing for greater energy dispersal

Which statement concerning spontaneous chemical reactions is true?

Spontaneous reactions are those that occur without an ongoing outside source of energy.

For the reaction shown below, ΔG°rxn is 142 kJ. In which direction is the reaction spontaneous at 25°C, when the pressures of SO2, O2, and SO3 are 0.1 atm, 0.2 atm, and 1 × 10−4 atm, respectively? 2 SO2(g) + O2(g) → 2 SO3(g)

The reverse reaction is spontaneous under these conditions.

Consider a reaction where ΔS rxn = −315 J/K and ΔH rxn = −45.6 kJ. Which statement is true about the spontaneity of this reaction?

This reaction is nonspontaneous at 25°C but will become spontaneous if the temperature is decreased to −130°C.

For which of the processes below will ΔS be a positive number? 1) CH4(g) → CH4(l) 2) N2H4(g) → N2(g) + 2H2(g) 3) H2O(s) → H2O(g)

both 2 and 3

ΔG rxn depends on both ΔH rxn and ΔS rxn. For which conditions of ΔH rxn and ΔS rxn will a reaction always be spontaneous?

when ΔH rxn is negative and ΔS rxn is positive

For the reaction below, what can you conclude about ΔG°rxn for the reaction? H2(g) + Br2(g) ⇄ 2 HBr(g) K = 2 × 1019 (at 25°C)

ΔG°rxn < 0

What are the signs of ΔS univ, ΔS surr, and ΔS sys, respectively, for water freezing at −10°C?

ΔS univ is positive, ΔS surr is positive, and ΔS sys is negative.

What is the standard entropy change for the reaction below? 2 CO(g) + 2 NO(g) → N2(g) + 2 CO2(g) S° (CO(g)) = 197.7 J/(mol·K) S° (CO2(g)) = 213.8 J/(mol·K) S° (NO(g)) = 210.8 J/(mol·K) S° (N2(g)) = 191.6 J/(mol·K)

−197.8 J/K

Determine the standard free energy change for the reaction below. 2 CO(g) + 2 NO(g) → N2(g) + 2 CO2(g) ΔG°f (CO(g)) = −137.2 kJ/mol ΔG°f (CO2(g)) = −394.4 kJ/mol ΔG°f (NO(g)) = 97.6 kJ/mol

−709.6 kJ