In the thermite reaction $$\ce{2Al(s) + Fe2O3(s) -> 2Fe(l) + Al2O3(s)}$$ what is the maximum temperature attainable by the products? Assume reactants at $25\ \mathrm{^\circ C}$ and $1\ \mathrm{atm}$ and that all heat capacities remain constant.
I started by using Hess's law to find the enthalpy change of the reaction. I couldn't find a heat of formation for liquid iron so I assume I have to find that out. I just wrote out the equation $$\ce{Fe(s) + heat + enthalpy of fusion -> Fe(s)}$$ and figured the heat of formation for liquid iron at $25\ \mathrm{^\circ C}$ is around $-302.71\ \mathrm{kJ/mol}$.
To find the max temperature I used $$\Delta H_\mathrm r=\Delta T\cdot C_\mathrm p(\text{products})$$ and came out with an equation like $$-14445\ \mathrm{kJ/mol}=0.147\ \mathrm{kJ/(mol\ K)}\cdot T_\text{max}$$ This gives me a negative temperature, so I assume it is wrong. Even if I were to take the absolute value, the answer seems awfully high. I was expecting something around a few thousand degrees not near ten thousand.
No comments:
Post a Comment