Holooly Plus Logo
Holooly Plus Logo

Question 23.2: The molar enthalpy of fusion of water is ΔHfus = 6.01 kJ·mol......

The molar enthalpy of fusion of water is ΔH_{fus} = 6.01\ kJ·mol^{–1} at 0°C, and the molar enthalpy of vaporization of water is ΔH_{vap} = 40.65\ kJ·mol^{–1} at 100°C. Calculate the values of ΔS_{fus} and ΔS_{vap} for water at these two phase transitions at a constant pressure of one atm.

Step-by-Step
The 'Blue Check Mark' means that this solution was answered by an expert.
Learn more on how do we answer questions.
Report Answer

The value of ΔS_{fus} is calculated using Equation 23.8. The melting point of water is 0°C, or 273.15 K; so we have

ΔS_{fus}=\frac{∆H_{fus}}{T_{m}} =\frac{6.01 × 10^3\ J·mol^{–1}}{273.15\ K} = 22.0\ J·K^{–1}·mol^{–1}

The value of ΔS_{vap} is calculated using Equation 23.9, with T_{b} = 373.15\ K:

ΔS_{vap}=\frac{∆H_{vap}}{T_{b}} =\frac{40.65× 10^3\ J·mol^{–1}}{373.15\ K} = 108.9\ J·K^{–1}·mol^{–1}

Notice that both ΔS_{fus} and ΔS_{vap} are positive, and \Delta S_{vap} > \Delta S_{fus}.

Related Answered Questions

Question: 23.10

Will the reaction described by the equation CO(g, 0.010 bar) + 2 H2(g, 0.010 bar) → CH3OH(l) occur spontaneously at 25°C? ...

Verified Answer:

We first use Table 23.1 to calculate ΔG^{\c...
Question: 23.9

Calculate the values of ΔG°rxn and K at 25°C for the equation PCl3(g) + Cl2(g) ⇋ PCl5(g) ...

Verified Answer:

Application of Equation 23.26 to this equation yie...
Question: 23.1

Predict the sign of the entropy change, ΔSsys, for the following processes: (a) H2O(g) (1 bar, 25°C) → H2O(g) (0.01 bar, 25°C) (b) The dissolution of sodium chloride in water (c) NaCl(aq) (4.8 M, 20°C) → NaCl(aq) (1.0 M, 20°C) (d) C6H6(g) (10 Torr, 25°C) → C6H6 (adsorbed on a metal surface at 25°C) ...

Verified Answer:

(a)  A gas at a lower pressure, and thus with grea...
Question: 23.3

Without referring to Table 23.1, arrange the following molecules in order of increasing standard molar entropy: CH2Cl2(g); CHCl3(g); CH3Cl(g). ...

Verified Answer:

The number of atoms is the same in each case, but ...
Question: 23.11

One step in the conversion of coal to liquid fuels involves the reaction between H2(g) and CO(g) to produce methanol, CH3OH(g). CO(g) + 2 H2(g) ⇌ CH3OH(g) ΔH°rxn = –90.5 kJ·mol^–1 (23.29) The equilibrium constant at 25°C for this chemical equation is K = 2.5 × 10^4. Calculate the value of K at ...

Verified Answer:

We can apply the van’t Hoff equation (Equation 23....
Question: 23.8

The value of K for the equation AgCl(s) ⇋ Ag^+(aq) + Cl^–(aq) (23.23) is 1.8 × 10^−10 at 25°C. Calculate the value of ΔGrxn at 25°C for the equation Ag^+(aq, 0.10 M) + Cl^−(aq, 0.30 M) → AgCl(s) (23.24) ...

Verified Answer:

Equation 23.24 is the reverse of Equation 23.23, s...
Question: 23.7

The thermodynamic equilibrium constant at 25°C for the chemical equation CH3COOH(aq) + H2O(l) ⇋ H3O^+(aq) + CH3COO^−(aq) is K = 1.8 × 10^−5. Calculate the value of ΔG°rxn at 25°C. ...

Verified Answer:

The value of ΔG^{\circ}_{rxn} can b...
Question: 23.6

The value of Kc for the equation CH3COO^–(aq) + H2O(l) ⇋ CH3COOH(aq) + OH^−(aq) is 5.6 × 10^–10 M at 25°C. Determine the value of the thermodynamic equilibrium constant, K, for this equation. ...

Verified Answer:

In this case, Q^{\circ}_{c} = 1\ M,...
Question: 23.5

The reaction system described by the chemical equation 2HI(g) ⇋ H2(g) + I2(g) is prepared at 598 K with the initial pressures PHI = 0.500 bar, PH2 = 0.150 bar, and PI2= 4.25 × 10^–2 bar. Given that Kp = 1.08 × 10^–2 at 598 K, calculate the value of ΔGrxn for this reaction system and indicate in ...

Verified Answer:

The value of Q_{p} for this equatio...
Question: 23.4

Predict under what conditions the following processes will be spontaneous: (a) Br2(l) → Br2(g) (b) CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) (c) Ar(g, 1L) → Ar(g, 2L) (free expansion at constant T) (d) 3 O2(g) → 2 O3(g) (endothermic) ...

Verified Answer:

(a) The vaporization of bromine requires an input ...