Answer the following questions using the chemical reaction and thermochemical in

Question

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



Br2(g) + C5H8(g) 1C5H6(g) + 2HBr(g)

1. Determine G°rx (in kJ) for this reaction at 1212 K. Assume H°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.

Hf° (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

Explanation / Answer

G = H - TS

First calcualte the dG for all substituents:

C5H56:

G = H – TS

G = 139 – 1212 *0.27447

G =-193.66

HBr:

G = H – TS

G = - 36.29 – 1212 *0.19870

G =-277.11

Br2:

G = H – TS

G = 30.9 – 1212 *0.2455

G =-266.65

C5H8:

G = H – TS

G = 36.0 – 1212 *0.28966

G =-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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