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Entropy for a Reversible Process

Acetic acid f...

Question

Acetic acid forms a dimer in the gas phase
The dimer is held together by two hydrogen bonds with a total strength of 66.5 kJ per mole of dimer. At $25^{o} C,$ the equilibrium constant for the dimerisation is $1.3 \times 10^{3}$ (pressure in atm). What is magnitude $△ S^{0}$ for the reaction? Assume that $△ H$ does not vary with temperature.

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Solution

$2 C H_{3} C O O H (g) \to (C H_{3} C O O H)_{2} (g)$
$△ G^{o} - - 2.303 R T l o g K$
$△ G^{o} = - 2.303 \times 8.314 \times 298 \times l o g (1.3 \times 10^{3}) = - 17767.69 J = - 17.77 k J$

Again,
$△ G^{0} = △ H^{0} - T △ S^{0}$
$- 17.77 = - 66.5 - 298 \times △ S^{0}$
$△ S^{0}$ = $(\frac{- 66.5 + 17.77}{298})$
$△ S^{0}$ = $(\frac{- 48.73}{298}) = - 0.163 k J m o l^{- 1} K^{- 1}$
Therefore, $△ S^{o} = - 0.163 k J m o l^{- 1} K^{- 1}$

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Similar questions

Q. Acetic acid forms dimer in vapour phase. The dimer is held together by two hydrogen bonds with a total strength of

66.5

kJ per mole of dimer. If at

25^{o}

C, the equilibrium constant for the dimerization is

1.3 \times 10^{3}

Δ S^{o}

for the reaction

2 C H_{3} C O O H ⇌ (C H_{3} C O O H)_{2}

l o g 1.3 = 0.1139

C H_{3} C O O H

can form a dimer

(C H_{3} C O O H)_{2}

in the gas phase. The dimer is held together by two H-bonds with a total strenght of 66.5 kJ per mol of dimer

25^{o} C,

the equilibrium constant for the dimerization is

1.3 \times 10^{3} .

△ S^{o}

for the reaction:

2 C H_{3} C O O H (g) ⇌ (C H_{3} C O O H)_{2} (g)

C H_{3} C O O H

can form a dimer

(C H_{3} C O O H)_{2}

in the gas phase. The dimer is held together by two H-bonds with a total strenght of 66.5 kJ per mol of dimer

25^{o} C,

the equilibrium constant for the dimerization is

1.3 \times 10^{3} .

△ S^{o}

for the reaction:

2 C H_{3} C O O H (g) ⇌ (C H_{3} C O O H)_{2} (g)

{C H}_{3} C O O H

can form a dimer

{({C H}_{3} C O O H)}_{2}

in the gas phase. The dimer is held together by two H-bonds with a total strength of

66.5 k J

per mol of the dimer.

25^{o} C

, the equilibrium constant for the dimerization is

1.3 \times 10^{3}

Δ S^{o}

for the reaction:

2 {C H}_{3} C O O H (g) ⇌ {({C H}_{3} C O O H)}_{2} (g)

C H_{3} C O O H

can form a dimer

(C H_{3} C O O H)_{2}

in the gas phase. The dimer is held together by two H - bonds with a total strength of

77.43 k J p e r m o l

27^{\circ} C

, the equilibrium constant for the dimerization is

1.096 \times 10^{3}

, then calculate the magnitude of

Δ S^{\circ}

k J

) for the reaction:

2 C H_{3} C O O H (g) ⇌ (C H_{3} C O O H)_{2} (g)

(Round upto 2 digits after decimal and

ln (1.096 \times 10^{3}) \approx 7 a n d R = 8.3 J K^{- 1} m o l^{- 1}

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