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From the following data, calculate the enthalpy change for the combustion of cyclopropane at 298 K. The enthalpy of formation of CO_(2)(g), H_(2)O(l) and propene (g) are - 393.5, -285.8 and 20.42 kJ"mol"^(-1) respectively.The enthalpy of isomerisation of cyclopropane to propene is -33.0 kJ"mol"^(-1). |
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Answer» Solution :The given equations are : (i) `C(s) + O_(2)(g) to CO_(2)(g) DELTAH = -393.5 kJ` (ii) `H_(2)(g) + 1/2 O_(2)(g) to H_(2)O(l) DeltaH = -285.8 kJ` (iii) `3C(s) + 3H_(2)(g) to C_(3)H_(6)(g) DeltaH = 20.42 kJ` (iv)  The required equation(v) can be obtained by multiplying equation(i) and (ii) by 3 and adding these, then subtracting equation(ii) from these and adding equation(iv), i.e `DeltaH = [Eq.(i) xx 3] + [Eq.(ii) xx 3] - [Eq.(iii)] + [Eq.(iv)]` `= (-395.5 xx 3)+(-285.8 xx 3) - (20.42) + (-33.0)` ` = -2091.32 kJ` |
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