Problem: Dry chemical hand warmers utilize the oxidation of iron to form iron oxide according to the following reaction: 4 Fe(s) + 3O2(g) → 2Fe2O3(s)Standard thermodynamic quantities for selected substances at 25 o m C Reactant or productΔH°f (kJ/mol)Fe(s)0.0O2(g)0.0Fe2O3(s)-824.2  Calculate how much heat (in kilojoules) a hand warmer containing 21.0 g of iron powder produces.

FREE Expert Solution

We are asked to calculate how much heat (in kilojoules) a hand warmer containing 21.0 g of iron powder produces.


ΔH°rxn=ΔH°f, prod-ΔH°f, react


Note that we need to multiply each ΔH˚f by the stoichiometric coefficient since ΔH˚f is in kJ/mol. 

Also, note that ΔH˚f for elements in their standard state is 0.


ΔH°rxn=ΔH°f, prod-ΔH°f, reactΔH°rxn=(2(-824.2 kJ))-(4(0 kJ)+3(0 kJ))

ΔH°rxn = 1648.4 kJ 


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Problem Details

Dry chemical hand warmers utilize the oxidation of iron to form iron oxide according to the following reaction:

 4 Fe(s) + 3O2(g) → 2Fe2O3(s)

Standard thermodynamic quantities for selected substances at 25 o m C 


Reactant or productΔH°f (kJ/mol)
Fe(s)
0.0
O2(g)
0.0
Fe2O3(s)
-824.2

 

 


Calculate how much heat (in kilojoules) a hand warmer containing 21.0 g of iron powder produces.

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