Question

Given..... `C_6H_14(l) +19/2O_2(g)rarr 6CO_2(g) + 7H_2O(l)+3854.9*kJ` How do I calculate `DeltaH_f^@` for hexanes?

Answer 1

You cannot calculate `DeltaH_f^@` from these data...

Explanation:

We want to calculate `DeltaH_f^@` for hexanes...the which by definition, is the enthalpy change when one mole of stuff is formed from its constituent elements in their standard states under standard conditions....

`6C(s)+7H_2(g)rarrC_6H_14(l)+DeltaH^@` `;DeltaH_"rxn"^@=DeltaH_f^@"hexane"`

We were given enthalpy data for the combustion reaction...

`C_6H_14(l) +19/2O_2(g)rarr 6CO_2(g) + 7H_2O(l)+3854.9*kJ`

In order to assess `DeltaH_f^@` for hexanes, we need `DeltaH_f^@` for water, and `DeltaH_f^@` for carbon dioxide....