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How much energy is evolved during the reaction of 48.7 g of Al, according to the reaction below? Assume that there is excess Fe2O3. Fe2O3(s) + 2 Al(s) → Al2O3(s) + 2 Fe(s) ΔH°rxn = - 852 kJ

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barnuts

From the reaction, we see that for every 2 moles of Al reacted, 852 kJ of energy is released. So convert the mass given to moles:

moles Al = 48.7 g / (26.98 g/mol)

moles Al = 1.805 mol

 

So the energy evolved is:

Energy = -852 kJ / 2 mol * 1.805 mol

Energy = -769 kJ