Question

Answer the following questions using the chemical reaction and thermochemical information given below: Br2(g) + C5H8(g)...

Answer the following questions using the chemical reaction and thermochemical information given below:

Br2(g) + C5H8(g) ⇌ 1C5H6(g) + 2HBr(g)

 ΔHf° (kJ/mol) S° (J mol-1 K-1) C5H6 139.00 274.47 HBr -36.29 198.70 Br2 30.9 245.5 C5H8 36.00 289.66

1. Determine ΔG°rx (in kJ) for this reaction at 1212 K. Assume ΔH°f and S° do not vary as a function of temperature. Report your answer to two decimal places 2. Determine the equilibrium constant for this reaction. Report your answer to three significant figures in scientific notation.

2. Determine the equilibrium constant for this reaction. Report your answer to three significant figures in scientific notation.

Homework Answers

Answer #1

ΔG = ΔH - TΔS

First calcualte the dG for all substituents:

C5H56:

ΔG = ΔH – TΔS

ΔG = 139 – 1212 *0.27447

ΔG =-193.66

HBr:

ΔG = ΔH – TΔS

ΔG = - 36.29 – 1212 *0.19870

ΔG =-277.11

Br2:

ΔG = ΔH – TΔS

ΔG = 30.9 – 1212 *0.2455

ΔG =-266.65

C5H8:

ΔG = ΔH – TΔS

ΔG = 36.0 – 1212 *0.28966

ΔG =-315.1

Now calculate the dG for the recation:

delta G(rxn) = delta G(products) - delta G(reactants)

Br2(g) + C5H8(g) ⇌ 1C5H6(g) + 2HBr(g)
delta G(rxn) = delta G(=-193.66 +2*-277.11 ) - delta G(-266.65 ) +(-315.1) kJ/mol

delta G(rxn) =-747.88 +581.75 kJ/mol

= -166.13 kJ/mol

= -166 kJ/mol

delta G = -RTlnK

-166000 J = (-8.31 J / mole K)(1212 K)(ln K)
16.48 =ln K
K = e^16.48= 1.4 x 10^7

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