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Determine standard heat of formation of `MnO_(2)` from the following data : `2Al(s)+(3)/(2) O_(2)(g) to Al_(2)O_(3)(s),DeltaH^(0)= -1670 kJ`
`3MnO_(2)(s)+4Al(s) to 3 Mn(s)+2Al_(2)O_(3)(s), Delta H^(0)= - 1792 kJ`

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`2Al(s)+(3)/(2)O_(2)(g) to Al_(2)O_(3)(s), Delta H^(0) = - 1670 kJ` ..[1]
`3MnO_(2)(s)+4Al(s) to 3Mn(s)+2Al_(2)O_(3)(s), Delta H^(0)= - 1792 kJ` ..[2]
`2xx eq. [1]-1 xx eq.[2]` we have,
`3Mn(s)+3O_(2)(g) to 3MnO_(2)(s)`
`Delta H^(0)= [2(-1670)-1(-1792)] kJ= - 1548 kJ`
`Mn(s)+O_(2)to MnO_(2)(s), Delta H^(0)= -(1)/(3)xx1548= -516 kJ`
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