Thermodynamics

Thermodynamics

Question

The enthalpy changes for the following processes are listed below:
Cl2(g) = 2Cl(g), 242.3 kJ mol–1
I2(g) = 2I(g), 151.0 kJ mol–1
ICl(g) = I(g) + Cl(g), 211.3 kJ mol–1
I2(s) = I2(g), 62.76 kJ mol–1
Given that the standard states for iodine and chlorine are I2(s) and Cl2(g), the standard enthalpy of formation for ICl(g) is

  • –14.6 kJ mol–1

  • –16.8 kJ mol–1

  • +16.8 kJ mol–1

  • +244.8 kJ mol–1

Answer

C.

+16.8 kJ mol–1

1 half straight I subscript 2 space left parenthesis straight s right parenthesis space space plus 1 half space Cl subscript 2 space rightwards arrow with space on top space ICl space left parenthesis straight g right parenthesis
increment straight H space equals space open square brackets 1 half increment straight H subscript straight I subscript 2 left parenthesis straight s right parenthesis space rightwards arrow straight I subscript 2 left parenthesis straight g right parenthesis end subscript space plus space 1 half straight mu subscript straight I minus straight I end subscript space plus 1 half straight mu subscript Cl minus Cl end subscript close square brackets space minus space left square bracket straight mu subscript straight I minus Cl end subscript right square bracket
space space equals open parentheses 1 half space straight x space 62.76 space space plus 1 half space straight x space 151.0 space plus 1 half space straight x space 242.3 close parentheses space minus left parenthesis 211.3 right parenthesis
space equals space 228.03 space minus 211.3
increment straight H space equals space 16.73

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