Multiple Choice
Calculate ΔS°rxn for the reaction: 2NO(g) + O2(g) → 2NO2(g) given the standard molar entropies: S°(NO) = 210.7 J/mol·K, S°(O2) = 205.0 J/mol·K, S°(NO2) = 240.1 J/mol·K.
19. Chemical Thermodynamics
Entropy Calculations
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The entropy change associated with the expansion of one mole of an ideal gas from an initial volume of V_i to a final volume of V_f at constant temperature is given by the equation, ΔS = R ln (V_f/V_i). If V_i = 2.0 L and V_f = 4.0 L, what is the entropy change associated with the expansion?
A
ΔS = R ln(4)
B
ΔS = R ln(0.5)
C
ΔS = R ln(1)
D
ΔS = R ln(2)
Verified step by step guidance1
Identify the formula for the entropy change of an ideal gas during expansion at constant temperature: ΔS = R ln(V_f/V_i).
Substitute the given initial volume (V_i = 2.0 L) and final volume (V_f = 4.0 L) into the formula.
Calculate the ratio of the final volume to the initial volume: V_f/V_i = 4.0 L / 2.0 L.
Simplify the ratio to find the value inside the natural logarithm: V_f/V_i = 2.
Substitute the simplified ratio into the formula: ΔS = R ln(2).
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