Since 1891 lighting lamps have been manufactured in the Netherlands. The improvement today in comparisonto 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. Give a thermochemical cycle (law of Hess) for sublimation of CeBr_(3) , via vapour of mononucler ions (H_(1) =H_("lattice"), H_(e) = H_("electrostatic"), H_(s) =H_("sublimation") , H is not absolute , H means DeltaH) H_(s)=-H_(1) + H_(e) The lattice energy of the solid can be calculatedusing the Baron -Lande formula, H_(1)=d(Z+Z-Ae^(2))/(r_(+) +r_(-))(1-(1)/(n)) The factorFe^(2) (necessary in order to calculate the lattice is 2.985. The Borm exponent n is 11. The charge of the ions Z_(+) and Z_(_) are integer number (Z is negative ). For the calculation of the energy of gaseous CeBr_(3) (when formed from ions) the same Born- Lande formula can be used without A. The structure of CeBr_(3) in the gas phase is planer triangular . The radius of Ce^(3+) is 0.115 nm and of Br is 0.182nm.

Since 1891 lighting lamps have been manufactured in the Netherlands. T

1.	Since 1891 lighting lamps have been manufactured in the Netherlands. The improvement today in comparisonto 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. Give a thermochemical cycle (law of Hess) for sublimation of CeBr_(3) , via vapour of mononucler ions (H_(1) =H_("lattice"), H_(e) = H_("electrostatic"), H_(s) =H_("sublimation") , H is not absolute , H means DeltaH) H_(s)=-H_(1) + H_(e) The lattice energy of the solid can be calculatedusing the Baron -Lande formula, H_(1)=d(Z+Z-Ae^(2))/(r_(+) +r_(-))(1-(1)/(n)) The factorFe^(2) (necessary in order to calculate the lattice is 2.985. The Borm exponent n is 11. The charge of the ions Z_(+) and Z_(_) are integer number (Z is negative ). For the calculation of the energy of gaseous CeBr_(3) (when formed from ions) the same Born- Lande formula can be used without A. The structure of CeBr_(3) in the gas phase is planer triangular . The radius of Ce^(3+) is 0.115 nm and of Br is 0.182nm.
Answer» SOLUTION :N//A