Since 1891 lighting lamps have been manufactured in the Netherlands. The improvement today in comparison to the first lamp is enormous , especially with the intorduction of the gas discharge lamps. The life- time has increased by orders of magnitude . the colour is also an important aspect. Rare earth metal compunds like `CeBr_(3)` are now included to reach a colour temperature of 6000K in the lamp the compounds are ionic solids at room temperature , and upon heating they sublime partially to give a vapour of neutral metal halide molecules . To achieve a high vapour pressure, the sublimation enthalpy should be as low as possible.
Conclusion in relation to the previous answers. was adding CsBr a good idea ? Mark the correct answer.
`implies` Adding CsBr is counterproductive.
`implies` Adding CsBr has no influence
`implies` Adding CsBr is advantageous
`implies` From these data no clear answer can be given.

Answer

Steps 1 : The lattice energy of `CsCeBr_(4)` with opposite sign is:
`H_(1) =(139xx1xx1xx1.75)/(0.617) xx(10)/(11) KJ "mol"^(-1)`
step 2:
`H_(2) = 4 xx(139.3.1)/(0.297)(10)/(11) -6 xx(139 xx1xx1)/(0.297 xx (2)/(3)xx sqrt(6) xx(10)/(11) KJ "mol"^(-1) = 3543 KJ "mol"^(-1)`
Step 3 : The electronic energy in the gas phase of `CeBr_(3)` is (see answer 8.2):
`H_(3) =-3xx(139xx 1xx1)/(0.297 xx sqrt(3))xx(10)/(11) KJ "mol"^(-1) =- 3092 KJ "mol"^(-1)`
Step 4 : The electrostatic energy in the gas phase of CsBr is
`H_(4) =-(139xx1xx1)/(0.363) xx(10)/(11) KJ mol^(-1) =-348 KJ "mol"^(-1)`
Total sum .
`H_("total") = H_(1) + H_(2) + H_(3) +H_(4) =461 KJ "mol"^(-1)`