Question

Dry chemical hand warmers utilize the oxidation of iron to form iron oxide according to the following reaction: Part A 4Fe(s) + 3O2(g) 2Fe2O3(s) Standard thermodynamic quantities for selected substances at 25°C Calculate how much heat (in kilojoules) a hand warmer containing 28.0 g of iron powder produces. Express the energy in kilojoules to three significant figures. Reactant or product AH; (kJ/mol) EVO AQ R o 2 ? 0.0 Fe(s) O2(g) Fe2O3(s) 0.0 —824.2 k. Submit Previous Answers Request Answer You may want to roforonco

Answer 1

Given:
Hof(Fe(s)) = 0.0 KJ/mol
Hof(O2(g)) = 0.0 KJ/mol
Hof(Fe2O3(s)) = -824.2 KJ/mol

Balanced chemical equation is:
4 Fe(s) + 3 O2(g) ---> 2 Fe2O3(s)

ΔHo rxn = 2*Hof(Fe2O3(s)) - 4*Hof( Fe(s)) - 3*Hof(O2(g))
ΔHo rxn = 2*(-824.2) - 4*(0.0) - 3*(0.0)
ΔHo rxn = -1648.4 KJ

Molar mass of Fe = 55.85 g/mol


mass(Fe)= 28.0 g

use:
number of mol of Fe,
n = mass of Fe/molar mass of Fe
=(28 g)/(55.85 g/mol)
= 0.5013 mol
Since Δ H is negative, heat is released
when 4 mol of Fe reacts, heat released = 1648.4 KJ
So,
for 0.5013 mol of Fe, heat released = 0.5013*1648.4/4 KJ
= 207 KJ
Answer: 207 KJ