For a hypothetical element, “Quintessium” (Q), which exists in different allotropic forms, one of them consists of dodecahedral units (dodecahedral is a regular shape with 20 corners and 12 faces).

With Q atoms at all 20 corners and all bonds are equivalent. Calculate the heat evolved at constant pressure (in KJ) per mole of Q atom undergoing the change into this allotropic form if the bond dissociation enthalpy of Q – Q bond is 400 KJ / mole?

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answer is 600.

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Detailed Solution

There is 1.5 Q – Q bond per atom. Hence,

$Δ H = - 1.5 \times 100 = - 600 k J / m o l e o f Q$

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