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Thermodynamics

Question
CBSEENCH11008431

Given that bond energy of H-H and Cl- Cl are 430 kJ mol-1 and 240 kJ mol-1 respectively and ΔHf for HCl is -90 kJ mol-1. Bond and ΔHf for HCl is -90 kJ mol-1.Bond enthalpy of HCl is:

  • 290 kJ mol-1

  • 380 kJ mol-1

  • 425 kJ mol-1

  • 425 kJ mol-1

Solution

B.

380 kJ mol-1

increment straight H subscript reaction space equals increment subscript straight H minus straight H end subscript space plus increment straight H subscript Cl minus Cl end subscript
minus 2 space increment straight H subscript HCl equals negative negative 90 space kJ
Or space increment straight H subscript straight H minus Cl end subscript space equals space fraction numerator 430 plus 240 minus left parenthesis negative 90 right parenthesis over denominator 2 end fraction
space equals space 760 over 2 space equals space 380 space kJ space mol to the power of negative 1 end exponent