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Rahim Nirmal De
Asked: 2022-11-10T02:09:15+05:30 In:

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.
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`)
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`H_(s)=-H_(1) + H_(e)`
The lattice energy of the solid can be calculated using the Baron -Lande formula,
`H_(1)=d(Z+Z-Ae^(2))/(r_(+) +r_(-))(1-(1)/(n))`
The factor `Fe^(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. 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.
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`)
image
`H_(s)=-H_(1) + H_(e)`
The lattice energy of the solid can be calculated using the Baron -Lande formula,
`H_(1)=d(Z+Z-Ae^(2))/(r_(+) +r_(-))(1-(1)/(n))`
The factor `Fe^(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.
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  1. Correct Answer – `(CeBr_(3))_(“glucose”) overset(-H_(1))rarr Ce^(3-) + 3Br^(-)`
    `Ce^(3+) + 3 Br overset(-He)rarr (CeBr_(3))_(“molecules”)
    ___________ `(CeBr_(3))_(“tattice”) overset(+H_(3)) rarr (CeBr_(3))_(“molecules”) ” “H_(3) =- H_91) + H_(e)`
    The lattice energy of the solid cn be calculated using the Boron – Lande formula:
    `H_(1) = d(Z_(+)Z_(-)Ae^(2))/(r_(+)+R_(-))(1-(1)/(n))`
    The factor `Fe_(2)` (necessary in order to calculate the lattice energy in KJ `”mol”^(-1)` ) amounts of 139 when the ionic radii are substituted in nm . The Madelung constant A for the lattice is 2.985. The Born 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-Londe formula can be used without A. The structure of `CeBr_(3)` in the gas phase is planar triangular . The radius of `Ce^(3+)` is 0.115 nm and of Br is 0.182 nm.

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Afreen Agarwal
Asked: 2022-11-09T22:16:26+05:30 In:

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.
Calculate the enthalpy of sublimation fo `CsCeBr_(4)` (in integers) Use the Born-Lande formula for all steps in the process and report the separate energies also (be aware of the signs). The `CeBr_(4)^(-)` anion is a teteahedron and in which the ratio between the edge and the destance between a corner of the tetrahedron and the centre of gravity (body – radius) amounts to `(2sqrt(6))//3 = 1.33` . The Born exponent of the CsBr is 11. The radius of Cs is 0.181 nm.

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.
Calculate the enthalpy of sublimation fo `CsCeBr_(4)` (in integers) Use the Born-Lande formula for all steps in the process and report the separate energies also (be aware of the signs). The `CeBr_(4)^(-)` anion is a teteahedron and in which the ratio between the edge and the destance between a corner of the tetrahedron and the centre of gravity (body – radius) amounts to `(2sqrt(6))//3 = 1.33` . The Born exponent of the CsBr is 11. The radius of Cs is 0.181 nm.
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  1. Correct 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)`

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Moti Mahmood Uppal
Asked: 2022-11-08T15:44:47+05:30 In:

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.
Calculate the enthalpy of sublimation of `CeBr_(3)` (in intergers, be aware of signs).
Attemps to make a better lamp have been undertaken by adding a stoichiometric amount of `CsBr` to the `CeBr_(3)` in the lamp leading at room temperature to solid `CsCeBr_(4)` lattice has a NaCl structure with Cs as cations and tetrahedral `CeBr_(4)^(-)` as complex anions. Sublimation of `CsCeBr_(4)` leads to a vapour of CsBr and `CeBr_(3)` molecules.

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.
Calculate the enthalpy of sublimation of `CeBr_(3)` (in intergers, be aware of signs).
Attemps to make a better lamp have been undertaken by adding a stoichiometric amount of `CsBr` to the `CeBr_(3)` in the lamp leading at room temperature to solid `CsCeBr_(4)` lattice has a NaCl structure with Cs as cations and tetrahedral `CeBr_(4)^(-)` as complex anions. Sublimation of `CsCeBr_(4)` leads to a vapour of CsBr and `CeBr_(3)` molecules.
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  1. Correct Answer – `H_(1) =- (139 xx 3xx1xx2.958)/(0.297) xx (10)/(11) KJ mol^(-1)`
    `H_(e) =(-3 xx(139xx3xx1)/(0.294)xx(10)/(11)) + (3 xx (139 xx1xx1)/(0.297sqrt(3))xx(10)/(11)) KJ “mol”^(-1) =-3092 KJ “mol”^(-1)`
    `H_(3) =(-3 xx(139 xx 3xx1)/(0.297)xx(10/(11)) + (3 xx (139 xx 1xx1)/(0.297 sqrt(3))xx (10)/(11)) KJ “mol”^(-1)`

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Sara Vig
Asked: 2022-11-08T09:46:30+05:30 In:

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.

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.
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  1. Correct Answer – The third answer is correctg : Adding CsBr is advantageous.

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Bishnu Narayan Buch
Asked: 2022-11-04T10:06:37+05:30 In:

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.
Give the reaction equations of the thermochemical cycle (Law of Hess) for this process in which some steps involve `CeBr_(4)^(-)` ions monmelecular ions and /or neutral molecules in the phase.
Step 1: `overset(+H_(1))rarr” “+`
Step 2 : `+” “overset(+H_(2)) rarr`
Step 3 : `+” “overset(+H_(3))rarr`
Step 4: `+” “overset(+H_(4))rarr`
Total : `(CsCeBr_(4))_(“lattice”) overset(+H_(“total”))rarr`
`(CeBr_(3))_(“molecules”) + (CsBr)_(“molecules”)`

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.
Give the reaction equations of the thermochemical cycle (Law of Hess) for this process in which some steps involve `CeBr_(4)^(-)` ions monmelecular ions and /or neutral molecules in the phase.
Step 1: `overset(+H_(1))rarr” “+`
Step 2 : `+” “overset(+H_(2)) rarr`
Step 3 : `+” “overset(+H_(3))rarr`
Step 4: `+” “overset(+H_(4))rarr`
Total : `(CsCeBr_(4))_(“lattice”) overset(+H_(“total”))rarr`
`(CeBr_(3))_(“molecules”) + (CsBr)_(“molecules”)`
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  1. Correct Answer – Step 1: (CsCeBr_(4))_(“lsttice” overset(+H_(1)) rarr Cs_(-) + CeBr_(4)^(-)`
    step 2: `CeBr_(4)^(-) overset(+H_(2))rarr Ce^(2+) + 4Br^(-)`
    Step 3: `Ce^(3+) + 3Br^(-) overset(+H_(3))rarr (CeBr_(3))_(“molecules”)`
    Steps 4 : `Cs^(-) z+ Br^(-) overset(+ H_(4)) rarr (CsBr)_(“molecules”)`
    _________ `(CsCeBr_(4))_(“lattice” overset(+total) rarr (CeBr_(3))_(“molecules”) + (CaBr)_(“molecules”)`

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