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Thermodynamics

Question
CBSEENCH11006191

Calculate the enthalpy change of reaction:
4 NH subscript 3 left parenthesis straight g right parenthesis space plus space 3 straight O subscript 2 left parenthesis straight g right parenthesis space space rightwards arrow space space space 6 straight H subscript 2 straight O left parenthesis straight l right parenthesis space plus 2 straight N subscript 2 left parenthesis straight g right parenthesis at 298K, given that the enthalpies of formation at 298 K for NH subscript 3 left parenthesis straight g right parenthesis space and space straight H subscript 2 straight O left parenthesis straight l right parenthesis space are space comma
minus 46.0 space and space minus 286.0 space kJ space mol to the power of negative 1 end exponent space respectively. space

Solution
space increment subscript straight f straight H to the power of 0 left parenthesis space for space the space reaction right parenthesis
space equals space sum from blank to blank of increment subscript straight f straight H to the power of 0 left parenthesis Products right parenthesis space minus space increment subscript straight f straight H to the power of 0 left parenthesis Reactants right parenthesis
equals space open square brackets 6 space cross times space increment subscript straight f straight H to the power of 0 left parenthesis straight H subscript 2 straight O right parenthesis space plus space 2 space cross times space increment subscript straight f straight H to the power of 0 left parenthesis straight N subscript 2 right parenthesis close square brackets
space equals space minus open square brackets 4 space cross times space increment subscript straight f straight H to the power of 0 space left parenthesis NH subscript 3 right parenthesis space plus space 3 space cross times space increment subscript straight f straight H to the power of 0 left parenthesis straight O subscript 2 right parenthesis close square brackets
space equals space open square brackets 6 space cross times space left parenthesis negative 286.0 right parenthesis plus 2 space cross times space zero close square brackets space
space space space space space space space space space space minus space open square brackets 4 space cross times space left parenthesis negative 46.0 right parenthesis space plus space 3 space cross times space zero close square brackets
space equals space minus 1716 plus space 184 space equals space minus 1532 space kJ