We’re being asked to determine the standard enthalpy formation (ΔH˚f) for B5H9.
Recall that ΔH˚rxn can be calculated from the enthalpy of formation (ΔH˚f) of the reactants and products involved:
Pentaborane B5H9(s) burns vigorously in O2 to give B2O3(s) and H2O(l):
2 B5H9(s) + 12 O2(g) ⟶5 B2O3(s) + 9 H2O(l)
The standard enthalpy change for this reaction is -9086.1 kJ. Given the following data, determine the standard enthalpy of formation for B5H9.
A. -1273.5 kJ mol-1
B. -846.1 kJ mol-1
C. 73.2 kJ mol-1
D. -2547.0 kJ mol-1
E. 146.4 kJ mol-1
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