An intimate mixture of ferric oxide and aluminium is used as solid rocket fuels-calculate fuel value per gram and fuel value per co of the mixture-heats of formation and densities are as follows-dHf al2o3- 399 kcal - moledhf fe2o3 -199 kcal - moledensity of fe2o3 -5-2 g - ccdensity of al -2-7 gm - ccsoln-2 al -3 - 202- al 203 eq 12 fe -3 - 202- fe2o3 eg 22 a l-f e 2 o 3-a l 2 o 3-2 f e1- eq 1-1- eq 2dh -399-199-200 kcalfuel value-gram2 moles of al -1 mol fe2o3 2 - 27-1 - 160214 gm- fuel value -gram -200 - 214-0-93 kcal - gmfuel gram- cc 2 mole of al -54 - 2-7-20 cc1 mole of fe2o3 -214 - 5-2-30-7 cc - - here- 1 mole of fe2o3 -160 - and 214 gm is the sumation of both al

Fe2O3 + 2AI → 2Fe + AI2O3 2*56 + 48 + 2*27 Heat of reaction = 399 – 199 = 200 kcal [Al amp; Fe are in their sta ...

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Standard XII

Chemistry

Introduction

an intimate m...

Question

an intimate mixture of ferric oxide and aluminium is used as solid rocket fuels.calculate fuel value per gram and fuel value per cc of the mixture.heats of formation and densities are as follows;

dHf al2o3= 399 kcal/mole
dhf fe2o3=199kcal/mole density of fe2o3=5.2g/cc density of al=2.7gm/cc

soln;-
2al +3/2 o2 -->al2o3 eq 1
2fe + 3/2 o2---- fe2o3 eg 2
2al +fe2o3= al2o3 + 2fe

1eq 1 - 1eq 2
dh=-399-(-199)
= -200 kcal

fuel value/gram
2 moles of al + 1 mol fe2o3
227 + 1 160
214gm

; fuel value /gram = 200/214= 0.93kcal/gm
fuel gram/ cc
2 mole of al= 54/2.7= 20cc
1 mole of fe2o3 = 214/5.2=30.7cc // here ,1 mole of fe2o3 = 160 ...... and 214gm is the sumation of both al
and fe2o3 ..... while if we multiply 30.7*5.2 =159.64 which is near about 160

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Solution

Fe₂O₃ + 2AI → 2Fe + AI₂O₃
256 + 48 + 227

Heat of reaction = 399 – 199 = 200 kcal [Al & Fe are in their standard states]

Total weight of reactans = 160 + 54 = 214 g

∴ Fuel value/gram = 200/214 = 0.9346 kcal/g Ans.

Volume of Al = 54/2.7 = 20 cc

Volume of Fe₂O₃ = 160/5.2 = 30.77 cc

Total volume = 20 + 30.77 = 50.77 cc

∴ Fuel value per cc = 200/50.77 = 3.94 kcal/cc

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