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    Gas-phase absolute entropy

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    1. Which molecule below should have the highest gas-phase absolute entropy at 25°C?

    a. CH4
    b. H2
    c. C2H6
    d. C2H4
    e. C2H2

    2. Some standard entropies (at 25°C in J/mol K) are given:
    Ca2+(aq) -55.2, F-(aq) -9.6, CaF2(s) +68.87. ΔS° for the reaction CaF2(s)  Ca2+(aq) + 2F-(aq) at 25°C in J/K is __________.

    a. -5.5
    b. -133.7
    c. +133.7
    d. -143.3
    e. +143.3

    3. Given the following table of thermodynamic data,
    substance S°

    C2H2 (g) 200.8 J/mol - K
    C2H4 (g) 219.4
    C2H6 (g) 229.5
    H2 (g) 130.58

    determine the ΔS° (in J/mol -K) for the reaction:

    C2H2 (g) + H2 (g)  C2H4 (g)

    a. -232.46
    b. +111.98
    c. +101.88
    d. -101.88
    e. -111.98

    4. The standard free energy of formation of __________ is zero.

    a. O (g)
    b. H2O (l)
    c. N2 (g) and O (g)
    d. N2 (g)
    e. Br2 (s)

    5. Consider the following table of thermodynamic data. All values are tabulated for 25°C.
    Substance ΔG°f (kJ/mol) S° (J/mol ? K)

    C2H2 (g) 209 201
    C2H4 (g) 68 219
    C2H6 (g) -33 230
    H2 (g) 0 131
    H2O (g) -229 189
    C2H5OH (l) -175 161

    What is the value of ΔH° (in kJ) for the reaction described below? Assume the reaction is performed at 25°C.

    C2H2 (g) + 2H2 (g)  C2H6 (g)

    a. -173
    b. -248
    c. -311
    d. 149
    e. 236

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    Solution Summary

    Multiple choice questions and corresponding answers to general chemistry inquiries, regarding gas-phase entropies, thermodynamic data, and energy formation.