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Dilithium is crucial to the propulsion s...

Dilithium is crucial to the propulsion system of some starships. Dilithium is fomred by the adhesion of two lithium atoms in the gas phase:
`Li(g)+Li(g)toLi_(2)(g)`
The enthalpy of formation of dilithium is not easily measurable by direct means. However, th following thermochemicalparameters are known.
`DeltaH_(f)^(@)` of `Li_(g)=150kJ//mol`
IE of `Li_(g)=5eV//"atom"[1eV//"atom"=100kJ//mol]`
`BE` of `Li_((g))^(+)=130kJ//mol`
`IE` of `Li_(2(g))=5eV//"molecule"`
`[IE=` ionisation energy] `[BE=` bond energy]
Q. What is `DeltaH_(f)^(@)` of `Li_(2(g))`?

A

`130kJ//mol`

B

`170kJ//mol`

C

`270kJ//mol`

D

`-270kJ//mol`

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The correct Answer is:
A
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Dilithium is crucial to the propulsion system of some starships. Dilithium is fomred by the adhesion of two lithium atoms in the gas phase: Li(g)+Li(g)toLi_(2)(g) The enthalpy of formation of dilithium is not easily measurable by direct means. However, th following thermochemicalparameters are known. DeltaH_(f)^(@) of Li_(g)=150kJ//mol IE of Li_(g)=5eV//"atom"[1eV//"atom"=100kJ//mol] BE of Li_((g))^(+)=130kJ//mol IE of Li_(2(g))=5eV//"molecule" [IE= ionisation energy] [BE= bond energy] Q. What is bond energy of Li_(2(g)) ?

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