A) Calculate H in kJ 2Al(s) + Fe2O3(s)-----> 2Fe(s)Al2O3(s) Usethe enthalpy chan

Question

A)   Calculate H in kJ        2Al(s) + Fe2O3(s)-----> 2Fe(s)Al2O3(s)               Usethe enthalpy changes for the combustion of Aluminum and iron:              2Al(s) + 1 1/2 O2(g) ------->Al2O3(s)     H= -1669.8 kJ              2Fe(s)+ 1 1/2 O2(g)--------------->Fe2O3(s)  H= -824.2 kJ B) What is the standard heat of reaction for the decompostionof hydrogen peroxide? 2H2O2 (l)-----------> 2H2O(l) +O2(g) A)   Calculate H in kJ        2Al(s) + Fe2O3(s)-----> 2Fe(s)Al2O3(s)               Usethe enthalpy changes for the combustion of Aluminum and iron:              2Al(s) + 1 1/2 O2(g) ------->Al2O3(s)     H= -1669.8 kJ              2Fe(s)+ 1 1/2 O2(g)--------------->Fe2O3(s)  H= -824.2 kJ B) What is the standard heat of reaction for the decompostionof hydrogen peroxide? 2H2O2 (l)-----------> 2H2O(l) +O2(g)

Explanation / Answer

Invert the second equation and add to first equation. Fe2O3(s)---------------> 2Fe(s)+ 1 1/2 O2(g)    H= + 824.2 kJ 2Al(s) + 1 1/2 O2(g) ------->Al2O3(s)     H= -1669.8 kJ -------------------------------------------- 2 Al + Fe2O3   -------> 2 Fe +Al2O3    H = -845.6 kJ 2H2O2 (l)-----------> 2H2O(l) +O2(g) H = products - reactants       = [ 2( Hf (H2O) +Hf(O2) ] - 2(Hf (H2O2))       = 2(-285.83) -2(-187.78)       = - 947.22 kJ 2H2O2 (l)-----------> 2H2O(l) +O2(g) H = products - reactants       = [ 2( Hf (H2O) +Hf(O2) ] - 2(Hf (H2O2))       = 2(-285.83) -2(-187.78)       = - 947.22 kJ

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