The third law of thermodynamics relates the entropy (randomness) of matter to it

Question

The third law of thermodynamics relates the entropy (randomness) of matter to its absolute temperature. Which of the following statements are in agreement with the third law of thermodynamics?

a) Select all that apply.

6) At zero kelvin, substances maximize entropy.

b) Calculate the standard-state entropy for the following reaction:

CH4(g)+2O2(g)?CO2(g)+2H2O(l)

The standard entropy values are given in the table.

1 ) As the temperature of a perfect crystal increases, the random vibrations of the molecules decrease. 2) In a gaseous state, the entropy of the system is zero. 3) In a crystalline state, there is a tendency to minimize entropy. 4) At absolute zero, the interatomic distance within a crystal is minimized. 5) At the melting point, the entropy of a system increases abruptly as the compound transforms into a liquid.

6) At zero kelvin, substances maximize entropy.

b) Calculate the standard-state entropy for the following reaction:

CH4(g)+2O2(g)?CO2(g)+2H2O(l)

The standard entropy values are given in the table.

Formula S?
J K?1 mol?1 CO2(g) 214 H2O(l) 189 CH4(g) 186 O2(g) 205

Explanation / Answer

1. In a crystalline state, there is a tendency to minimize entropy.

2. At absolute zero, the interatomic distance within a crystal is minimized.

3. At the melting point, the entropy of a system increases abruptly as the compound transforms into a liquid.

CH4(g)+2O2(g)?CO2(g)+2H2O(l)

Standard entropy change of reaction = stanadard entropies of product - standard entropies of reactant

st entropy chnage = [SCO2 + 2X SH2O] - [SCH4 + 2SO2] = 592 - 596 = -4 J K?1 mol?1

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