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Thermodynamics

Question
CBSEENCH11006297

Calculate the enthalpy change for the process
         CCl subscript 4 left parenthesis straight g right parenthesis space space space rightwards arrow space space straight C left parenthesis straight g right parenthesis space plus space 4 space Cl left parenthesis straight g right parenthesis
and calculate bond enthalpy of straight C minus Cl in CCl subscript 4 left parenthesis straight g right parenthesis.
increment subscript vap straight H to the power of 0 space left parenthesis CCl subscript 4 right parenthesis space equals space 30.5 space kJ space mol to the power of negative 1 end exponent
increment subscript straight f straight H to the power of 0 space left parenthesis CCl subscript 4 right parenthesis space equals space minus 135.5 space kJ space mol to the power of negative 1 end exponent
increment subscript straight a straight H to the power of 0 left parenthesis straight C right parenthesis space equals space 715.0 space kJ space mol to the power of negative 1 end exponent comma space where space increment subscript straight a straight H to the power of 0 space is space enthalpy space of space atomisation
increment subscript straight a straight H to the power of 0 left parenthesis Cl subscript 2 right parenthesis space equals space 242 space kJ space mol to the power of negative 1 end exponent

Solution

straight i right parenthesis space CCl subscript 4 left parenthesis straight l right parenthesis space rightwards arrow space CCl subscript 4 left parenthesis straight g right parenthesis space increment subscript vap straight H to the power of 0 space equals 30.5 space KJ space mol to the power of negative 1 end exponent
ii right parenthesis space straight C left parenthesis straight s right parenthesis space rightwards arrow straight C left parenthesis straight g right parenthesis increment subscript straight a straight H to the power of 0 space equals space 715.0 KJ space mol to the power of negative 1 end exponent
iii right parenthesis space Cl subscript 2 left parenthesis straight g right parenthesis rightwards arrow 2 Cl left parenthesis straight g right parenthesis space increment subscript straight a straight H to the power of 0 space equals 242 KJ space mol to the power of asterisk times minus 1 end exponent
iv right parenthesis space straight C left parenthesis straight g right parenthesis space plus 4 Cl left parenthesis straight g right parenthesis space rightwards arrow CCl subscript 4 left parenthesis straight g right parenthesis space
increment subscript straight f straight H equals negative 135.5 KJ space mol to the power of negative 1 end exponent

Enthalpy space change space for space the space give space CCl subscript 4 left parenthesis straight g right parenthesis space rightwards arrow straight C left parenthesis straight g right parenthesis space plus 4 Cl left parenthesis straight g right parenthesis
can space be space calculated space using space the space following space algebraic space calculation space as colon
equation space left parenthesis ii right parenthesis space plus 2 space straight x space equ left parenthesis Iii right parenthesis equals negative equ left parenthesis straight i right parenthesis minus equ left parenthesis iv right parenthesis
increment subscript straight a straight H to the power of 0 space left parenthesis straight C right parenthesis space plus space increment subscript straight a straight H to the power of 0 left parenthesis Cl subscript 2 right parenthesis minus increment subscript vap straight H to the power of 0 minus space increment subscript straight f straight H

equals left parenthesis 715.0 space KJ space mol to the power of negative 1 end exponent right parenthesis space plus 2 left parenthesis 242 space KJ space mol to the power of negative 1 end exponent right parenthesis space minus left parenthesis 30.5 space mol to the power of negative 1 end exponent right parenthesis minus
space space space space left parenthesis negative 135.5 KJ space mol to the power of negative 1 end exponent right parenthesis

therefore comma
increment straight H equals 1304 space KJ space mol to the power of negative 1 end exponent

Bond space enthalpy space of space straight C minus Cl space bond space in space CCl subscript 4 left parenthesis straight g right parenthesis
equals 1304 over 4 Kj space mol to the power of negative 1 end exponent
equals space 326 space KJ space mol to the power of negative 1 end exponent
straight i right parenthesis space CCl subscript 4 left parenthesis straight l right parenthesis space rightwards arrow space CCl subscript 4 left parenthesis straight g right parenthesis space increment subscript vap straight H to the power of 0 space equals 30.5 space KJ space mol to the power of negative 1 end exponent
ii right parenthesis space straight C left parenthesis straight s right parenthesis space rightwards arrow straight C left parenthesis straight g right parenthesis increment subscript straight a straight H to the power of 0 space equals space 715.0 KJ space mol to the power of negative 1 end exponent
iii right parenthesis space Cl subscript 2 left parenthesis straight g right parenthesis rightwards arrow 2 Cl left parenthesis straight g right parenthesis space increment subscript straight a straight H to the power of 0 space equals 242 KJ space mol to the power of asterisk times minus 1 end exponent
iv right parenthesis space straight C left parenthesis straight g right parenthesis space plus 4 Cl left parenthesis straight g right parenthesis space rightwards arrow CCl subscript 4 left parenthesis straight g right parenthesis space
increment subscript straight f straight H equals negative 135.5 KJ space mol to the power of negative 1 end exponent

Enthalpy space change space for space the space give space CCl subscript 4 left parenthesis straight g right parenthesis space rightwards arrow straight C left parenthesis straight g right parenthesis space plus 4 Cl left parenthesis straight g right parenthesis
can space be space calculated space using space the space following space algebraic space calculation space as colon
equation space left parenthesis ii right parenthesis space plus 2 space straight x space equ left parenthesis Iii right parenthesis equals negative equ left parenthesis straight i right parenthesis minus equ left parenthesis iv right parenthesis
increment subscript straight a straight H to the power of 0 space left parenthesis straight C right parenthesis space plus space increment subscript straight a straight H to the power of 0 left parenthesis Cl subscript 2 right parenthesis minus increment subscript vap straight H to the power of 0 minus space increment subscript straight f straight H

equals left parenthesis 715.0 space KJ space mol to the power of negative 1 end exponent right parenthesis space plus 2 left parenthesis 242 space KJ space mol to the power of negative 1 end exponent right parenthesis space minus left parenthesis 30.5 space mol to the power of negative 1 end exponent right parenthesis minus
space space space space left parenthesis negative 135.5 KJ space mol to the power of negative 1 end exponent right parenthesis

therefore comma
increment straight H equals 1304 space KJ space mol to the power of negative 1 end exponent

Bond space enthalpy space of space straight C minus Cl space bond space in space CCl subscript 4 left parenthesis straight g right parenthesis
equals 1304 over 4 Kj space mol to the power of negative 1 end exponent
equals space 326 space KJ space mol to the power of negative 1 end exponent