Question

Over the years, the thermite reaction has been used for welding railroad rails, in incendiary bombs, and to ignite solid-fuel rocket motors. The reaction is the following. MoO3(s) + 2 Al(s) → Mo(l) + Al2O3(s) What masses of molybdenum(VI) oxide and aluminum must be used to produce 14.3 g of molybdenum? What is the maximum mass of aluminum oxide that could be produced?

Answer 1

Atomic weight of MO= 96, Molecular weight of Oxygen =16, Atomic weight of aluminium =27

Molecular weight of MOO3= 96+3*16= 144 and that of Al2O3= 27*2+48= 102

Moles of molybdenum = 14.3/ 96= 0.149 moles

From the reaction MOO₃+ 2Al---->MO(l) +Al₂O₃(s)

1 mol of Mo requires 1moe of MOO3 and 2moles of Aluminium

Since Moles= mass/ molecular weight and mass =Molecular weight* moles

0.1489 moles of Mo requires 0.149 moles of MOO3=(0.149* 144gms =21.456 gms) and 2*0.149 moles of Al = (0.298*27gms= 8.05 gms of Al)

Maximum Amount of Al2O3 that can be formed= 0.149 moles* molecular weight of Al2O3= 0.149*102=15.2 gms