Question

The overall reaction in a commercial heat pack can be represented as 4Fe(s) + 3O_2 (g) right arrow 2Fe_2 O_3(s) delta H = -1652 kJ How much heat is released when 4.20 moles of iron are reacted with excess O_2? Heat = How much heat is released when 1.00 mole of Fe_2O_3 is produced? Heat = How much heal is released when 1.00 g iron is reacted with excess O_2? Heat= How much heat is released when l2.6 g Fe and 1.20 g O_2, are reacted? Heat =

Answer 1

a)

n = 4.2 mol of Fe react

-1652 kJ accoridng to the Hrxn based on 4 mol

b)

when 1 mol is produced,

since the Hrxn is based in 2 moles:

1/2*Hrxn = 1/2*-1652 = -826 kJ

c)

1 g of Fe

mol = masS/MW = 1/55.5 = 0.0180

Q = n*Hrxn = 0.0180*(-1652/4) = -7.434 kJ

d)

12.5 g of Fe burn

mol = 12.5/55.5 = 0.22727

Q = n*Hrxn = 0.22727*(-1652/4) = -93.86251 kJ