A mixture of metallic aluminium and Fe2O3 can be used for temperaturre welding..

Question

A mixture of metallic aluminium and Fe2O3 can be used for temperaturre welding...

3. A mixture of metallic aluminum and Fe20s can be used for high-temperature welding Two pieces of steel are placed end to end and the powdered mixture is applied and ignited. If the temperature desired is 3000°F and the heat loss is 20% of AHxn2sc + ??prod AHract) by radiation, what weight in pounds of the mixture (used in the molecular propor tions of 2Al 1Fe203) must be used to produce this temperature in 1 lb of steel to be welded? Assume that the starting temperature is 65°F. Cp, Liquid Cp, solid [Btu/(lb)(F)] 0.12 0.20 Heat of fusion (Btu/lb) Melting point (F) [Btu/(Ib)(F)] Data Fe and steel A1203 86.5 2800 0.25

Explanation / Answer

Answer:

a)
mass of Fe= 15 g
molar mass of Fe = 56 g/mol
number of moles of Fe = mass/molar mass
      = 15/56 mol
      = 0.268 mol

from reaction equation:
moles of Fe2O3 = moles of Fe/2
   =0.268/2
   =0.134 mol
molar mass of Fe2O3 = 159.7 g/mol
mass of Fe2O3 = number of moles * molar mass
   =0.134*159.7
   = 21.4g

moles of Al = moles of Fe
   = 0.268 mol
molar mass of Al = 27 g/mol
mass of Al = number of moles * molar mass
   = 0.268*27
   = 7.2 g

b)
From given reaction
moles of Al2O3 = moles of Fe/2
   =0.268/2
   =0.134 mol
molar mass of Al2O3 = 102 g/mol
mass of Fe2O3 = number of moles * molar mass
   = 0.134*102
   = 13.7g

c)
mass Al2O3 = 93% of maximum
   = 0.93*13.7
   = 12.7 g

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