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The first ionisation potential of Li is ...

The first ionisation potential of Li is `5.4` e V and the electron affinity of Cl is 3.6 eV . Calculate `Delta H` in kcal `mol^(-1)` for the reaction
`Li (g) + Cl (g) to Li^(+) + Cl^(-)`
Carried out at such low pressures that resulting ions do not combine with each other.

Text Solution

Verified by Experts

The overall reaction is written into two partial equations
`Li (g) to Li^(+) + e^(-) " " Delta E_(1) = 5.4 e V`
`Cl (g) + e^(-) to Cl^(-) " " Delta E_(2) = -3.6 e V `
`Delta H = Delta E_(1) - Delta E_(2) = 5.4 -3.6 = 1.8` e V
`=1.8 xx 23.06` kcal `mol^(-1)`
`=41.508` kcal `mol^(-1)`
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