Question

For a particular isomer of C8H18, the following reaction produces 5108.7 kJ of heat per mole of C8H18(g) consumed, under standard conditions.
What is the standard enthalpy of formation of this isomer of C8H18(g)?

Answer 1

Answer on Question #55348 - Chemistry - General chemistry

Question:

For a particular isomer of $C_8H_{18}$, the following reaction produces 5108.7 kJ of heat per mole of $C_8H_{18}(g)$ consumed, under standard conditions. What is the standard enthalpy of formation of this isomer of $C_8H_{18}(g)$?

Solution

$$\begin{array}{l} C_8H_{18}(g) + 25/2 O_2(g) = 8CO_2(g) + 9H_2O(g); \quad \Delta H_{\text{rxn}} = -5108.7 \, \text{kJ} \\ \quad \Delta H_{\text{rxn}} = 9\Delta H(H_2O) + 8\Delta H(CO_2) - \Delta H(C_8H_{18}) \\ \quad \Delta H(C_8H_{18}) = 9\Delta H(H_2O) + 8\Delta H(CO_2) - \Delta H_{\text{rxn}} \\ \quad \Delta H(C_8H_{18}) = 9(-241.8) + 8(-393.5) + 5108.7 = -215.5 \, \text{kJ/mol} \end{array}$$

Answer: $-215.5 \, \text{kJ/mol}$

www.AssignmentExpert.com