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Chapter 19: Problem 35

Does the entropy of the system increase, decrease, or stay the same when (a) a solid melts, (b) a gas liquefies, \((\mathbf{c})\) a solid sublimes?

Short Answer

Expert verified
(a) When a solid melts to become a liquid, the entropy of the system **increases** due to increased disorder and freedom of movement of particles. (b) When a gas liquefies, the entropy of the system **decreases** as the particles become more ordered and have less freedom of movement. (c) During sublimation, when a solid transitions directly into a gas, the entropy of the system **increases** due to the significant increase in disorder and freedom of movement.

Step by step solution

01

(a) Solid melts to Liquid

When a solid melts to become a liquid, the particles within the substance become more disordered and gain more freedom of movement. This means that the entropy of the system increases. So, when a solid melts, the **entropy increases**.
02

(b) Gas liquefies

When a gas condenses to become a liquid, the particles within the substance become more ordered and have less freedom of movement. This means that the entropy of the system decreases. So, when a gas liquefies, the **entropy decreases**.
03

(c) Solid sublimes

When a solid directly transitions into a gas (sublimation), the particles within the substance become significantly more disordered and have a huge increase in freedom of movement compared to the solid phase. This means that the entropy of the system increases. So, when a solid sublimes, the **entropy increases**.

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Most popular questions from this chapter

Use data from Appendix \(C\) to calculate the equilibrium constant, \(K,\) and \(\Delta G^{\circ}\) at \(298 \mathrm{~K}\) for each of the following reactions: (a) \(\mathrm{H}_{2}(g)+\mathrm{I}_{2}(g) \rightleftharpoons 2 \mathrm{HI}(g)\) (b) $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(g) \rightleftharpoons \mathrm{C}_{2} \mathrm{H}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g)$ (c) $3 \mathrm{C}_{2} \mathrm{H}_{2}(g) \rightleftharpoons \mathrm{C}_{6} \mathrm{H}_{6}(g)$

(a) What do you expect for the sign of \(\Delta S\) in a chemical reaction in which 3 mol of gaseous reactants are converted to 2 mol of gaseous products? (b) For which of the processes in Exercise 19.11 does the entropy of the system increase?

Consider what happens when a sample of the explosive TNT is detonated under atmospheric pressure. (a) Is the detonation a reversible process? (b) What is the sign of \(q\) for this process? (c) Is w positive, negative, or zero for the process?

Using data from Appendix \(\mathrm{C}\), write the equilibrium-constant expression and calculate the value of the equilibrium constant and the free- energy change for these reactions at \(298 \mathrm{~K}:\) (a) $\mathrm{NaHCO}_{3}(s) \rightleftharpoons \mathrm{NaOH}(s)+\mathrm{CO}_{2}(g)$ (b) $2 \mathrm{HBr}(g)+\mathrm{Cl}_{2}(g) \rightleftharpoons 2 \mathrm{HCl}(g)+\mathrm{Br}_{2}(g)$ (c) $2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{SO}_{3}(g)$

(a) What sign for \(\Delta S\) do you expect when the volume of 0.200 mol of an ideal gas at \(27^{\circ} \mathrm{C}\) is increased isothermally from an initial volume of \(10.0 \mathrm{~L} ?\) (b) If the final volume is \(18.5 \mathrm{~L},\) calculate the entropy change for the process. (c) Do you need to specify the temperature to calculate the entropy change?
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