1.

An intimate mixture of `Fe_(2)O_(3)` and `Al` is used in solid fuel rocket. `DeltaH` of `Al_(2)O_(3)` and `Fe_(2)O_(3)` are `399kcal` and `199kcal` respectively. Calculate the fuel value in `kcal g^(-1)` of mixture.

Answer» Correct Answer - 1
`2Al+Fe_(2)O_(3) rarr Al_(2)O_(3)+2Fe, DeltaH=?`
Given, `2Al+(3)/(2)O_(2)rarr Al_(2)O_(3),DeltaH=-399kcal ...(1)`
and `2Fe+(3)/(2)O_(2) rarr Fe_(2)O_(3), DeltaH=-199kcal ...(2)`
Subtracting `eq. (2)` from `eq. (10`
`underset(Fuel mixture)(2Al+Fe_(2)O_(3))rarr 2Fe=Al_(2)O_(3),DeltaH=-200kcal`
`Mol. wt. ` of fuel mixture `=2xx27+2xx56+48=214g`
`:. 214g `mixture produce `=200kcal `heat
`:. 1 g ` mixture produce `=(200)/(214)=0.9346~~1 kcal g^(-1)`


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