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| 1. |
Why are potassium and caesium rather than lithium used in photoelectric cells ? |
| Answer» Solution :The IONISATION enthalpy of lithium `(520 kJ mol^(-1))` is much higher than those of POTASSIUM `(419 kJ mol^(-1))`and caesium `(376 kJ mol^(-1))`. Due to high ionisation enthalpy, lithium does not emit electrons on EXPOSURE to light. On the other hand, potassium and caesium do so. Therefore, K and CS rather than Li are used in photoelectric cells. | |