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[Post New]22 Feb 2007 09:30:36 IST
    Subject: Re:Cs or Li ???
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Anurag.Seth (53)

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Hello Umang and Vasanth,

What is the energy of hydration?

Enthalpy of hydration, Hhyd, of an ion is the amount of energy released when a mole of the ion dissolves in a large amount of water forming an infinite dilute solution in the process, Mz+(g) + mH2O ® Mz+(aq) where Mz+(aq) represents ions surrounded by water molecules and dispersed in the solution. The approximate hydration energies of some typical ions are listed here. The table illustrates the point that as the atomic numbers increases, so do the ionic size, leading to a decrease in absolute values of enthalpy of hydration.
Enthalpy of Hydration (Hhyd kJ/mol) of Some Typical Ions
Ion Hhyd       Ion Hhyd       Ion Hhyd
H+ -1130 Al3+ -4665 Fe3+ -4430
--
Li+ -520 Be2+ -2494 F- -505
Na+ -406 Mg2+ -1921 Cl- -363
K+ -322 Ca2+ -1577 Br- -336
Rb+ -297 Sr2+ -1443 I- -295
Cs+ -276 Ba2+ -1305 ClO4- -238
--
Cr2+ -1904 Mn2+ -1841 Fe2+ -1946
Co2+ -1996 Ni2+ -2105 Cu2+ -2100
Zn2+ -2046 Cd2+ -1807 Hg2+ -1824
 
 Hence this the proof what vasanth has said and I too support,
And yes Li is more electropositive but oly in its solution,and not only Li; Rb and K are also more electropositive than Cs in their solutions.
Here is the table of SEP:
Half-reaction Eo (V)
Li+(aq) + e? ? Li(s) ?3.05
Rb+(aq) + e? ? Rb(s) ?2.98
K+(aq) + e? ? K(s) ?2.93
Cs+(aq) + e? ? Cs(s) ?2.92
Ba2+(aq) + 2e? ? Ba(s) ?2.91
Sr2+(aq) + 2e? ? Sr(s) ?2.89
Ca2+(aq) + 2e? ? Ca(s) ?2.76
Na+(aq) + e? ? Na(s) ?2.71
Mg2+(aq) + 2e? ? Mg(s) ?2.38
H2 + 2e? ? 2H? ?2.25
Be2+(aq) + 2e? ? Be(s) ?1.85
Al3+(aq) + 3e? ? Al(s) ?1.68
Ti2+(aq) + 2e? ? Ti(s) ?1.63
TiO(s) + 2H+ + 2e? ? Ti(s) + H2O ?1.31
Ti2O3(s) + 2H+ + 2e? ? 2TiO(s) + H2O ?1.23
Ti3+(aq) + 3e? ? Ti(s) ?1.21
Mn2+(aq) + 2e? ? Mn(s) ?1.18
V2+(aq) + 2e? ? V(s) ?1.13
Sn(s) + 4H+ + 4e? ? SnH4(g) ?1.07
SiO2(s) + 4H+ + 4e? ? Si(s) + 2H2O ?0.91
B(OH)3(aq) + 3H+ + 3e? ? B(s) + 3H2O ?0.89
TiO2+(aq) + 2H+ + 4e? ? Ti(s) + H2O ?0.86
2 H2O(l) + 2e- ? H2(g) + 2 OH-(aq) -0.83
Zn2+(aq) + 2e? ? Zn(s) ?0.76
Cr3+(aq) + 3e? ? Cr(s) ?0.74
Au(CN)2-(aq) + e- ? Au(s) +2 CN-(aq) -0.60
2TiO2(s) + 2H+ + 2e? ? Ti2O3(s) + H2O ?0.56
Ga3+(aq) + 3e? ? Ga(s) ?0.53
H3PO2(aq) + H+ + e? ? P(s) + 2H2O ?0.51
H3PO3(aq) + 3H+ + 3e? ? P(s) + 3H2O ?0.50
H3PO3(aq) + 2H+ + 2e? ? H3PO2(aq) + H2O ?0.50
Fe2+(aq) + 2e? ? Fe(s) ?0.44
2CO2(g) + 2H+(aq) + 2e- ? HOOCCOOH(aq) -0.43
Cr3+(aq) + e? ? Cr2+(aq) ?0.42
2H2O(l) + 2e- ? H2(g) + 2OH- [1.00x10-7mol L-1] -0.41
Cd2+(aq) + 2e? ? Cd(s) ?0.40
PbSO4(s) + 2e- ? Pb(s) +SO42-(aq) -0.36
GeO2(s) + 2H+ + 2e? ? GeO(s) + H2O ?0.37
In3+(aq) + 3e? ? In(s) ?0.34
Tl+(aq) + e? ? Tl(s) ?0.34
Ge(s) + 4H+ + 4e? ? GeH4(g) ?0.29
Co2+(aq) + 2e ? Co(s) ?0.28
H3PO4(aq) + 2H+ + 2e? ? H3PO3(aq) + H2O ?0.28
Ni2+(aq) + 2e? ? Ni(s) ?0.26
V3+(aq) + e? ? V2+(aq) ?0.26
As(s) + 3H+ + 3e? ? AsH3(g) ?0.23
MoO2(s) + 4H+ + 4e? ? Mo(s) + 2H2O ?0.15
Si(s) + 4H+ + 4e? ? SiH4(g) ?0.14
Sn2+(aq) + 2e? ? Sn(s) ?0.13
O2(g) + H+ + e? ? HO2?(aq) ?0.13
Pb2+(aq) + 2e? ? Pb(s) ?0.13
WO2(s) + 4H+ + 4e? ? W(s) ?0.12
CO2(g) + 2H+ + 2e? ? HCOOH(aq) ?0.11
Se(s) + 2H+ + 2e? ? H2Se(g) ?0.11
CO2(g) + 2H+ + 2e? ? CO(g) + H2O ?0.11
SnO(s) + 2H+ + 2e? ? Sn(s) + H2O ?0.10
SnO2(s) + 2H+ + 2e? ? SnO(s) + H2O ?0.09
WO3(aq) + 6H+ + 6e? ? W(s) ?0.09
P(s) + 3H+ + 3e? ? PH3(g) ?0.06
HCOOH(aq) + 2H+ + 2e? ? HCHO(aq) + H2O ?0.03
2H+(aq) + 2e? ? H2(g) 0.00
H2MoO4(aq) + 6H+ + 6e? ? Mo(s) + 4H2O +0.11
Ge4+(aq) + 4e? ? Ge(s) +0.12
C(s) + 4H+ + 4e? ? CH4(g) +0.13
HCHO(aq) + 2H+ + 2e? ? CH3OH(aq) +0.13
S(s) + 2H+ + 2e? ? H2S(g) +0.14
Sn4+(aq) + 2e? ? Sn2+(aq) +0.15
Cu2+(aq) + e? ? Cu+(aq) +0.16
HSO4?(aq) + 3H+ + 2e? ? SO2(aq) +0.16
SO42?(aq) + 4H+ + 2e? ? 2H2O(l) + SO2(aq) +0.17
SbO+ + 2H+ + 3e? ? Sb(s) + H2O +0.20
H3AsO3(aq) + 3H+ + 3e? ? As(s) + 3H2O +0.24
GeO(s) + 2H+ + 2e? ? Ge(s) + H2O +0.26
Bi3+(aq) + 3e? ? Bi(s) +0.32
VO2+(aq) + 2H+ + e? ? V3+(aq) +0.34
Cu2+(aq) + 2e? ? Cu(s) +0.34
[Fe(CN)6]3?(aq) + e? ? [Fe(CN)6]4?(aq) +0.36
O2(g) + 2H2O(l) + 4e- ? 4OH-(aq) +0.40
H2MoO4 + 6H+ + 3e? ? Mo3+(aq) +0.43
CH3OH(aq) + 2H+ + 2e? ? CH4(g) + H2O +0.50
SO2(aq) + 4H+ + 4e? ? S(s) + 2H2O +0.50
Cu+(aq) + e? ? Cu(s) +0.52
CO(g) + 2H+ + 2e? ? C(s) + H2O +0.52
I2(s) + 2e? ? 2I?(aq) +0.54
I3?(aq) + 2e? ? 3I?(aq) +0.54
[AuI4]?(aq) + 3e? ? Au(s) + 4I?(aq) +0.56
H3AsO4(aq) + 2H+ + 2e? ? H3AsO3(aq) + H2O +0.56
[AuI2]?(aq) + e? ? Au(s) + 2I?(aq) +0.58
MnO4-(aq) + 2H2O(l) + 3e- ? MnO2(s) + 4 OH-(aq) +0.59
S2O32? + 6H+ + 4e? ? 2S(s) + 3H2O +0.60
H2MoO4(aq) + 2H+ + 2e? ? MoO2(s) + 2H2O +0.65
O2(g) + 2H+ + 2e? ? H2O2(aq) +0.70
Tl3+(aq) + 3e? ? Tl(s) +0.72
H2SeO3(aq) + 4H+ + 4e? ? Se(s) + 3H2O +0.74
Fe3+(aq) + e? ? Fe2+(aq) +0.77
Hg22+(aq) + 2e? ? 2Hg(l) +0.80
Ag+(aq) + e? ? Ag(s) +0.80
NO3-(aq) + 2H+(aq) +e- ? NO2(g) + H2O(l) +0.80
[AuBr4]?(aq) + 3e? ? Au(s) + 4Br?(aq) +0.85
Hg2+(aq) + 2e? ? Hg(l) +0.85
MnO4?(aq) + H+ + e? ? HMnO4?(aq) +0.90
2Hg2+(aq) + 2e? ? Hg22+(aq) +0.91
[AuCl4]?(aq) + 3e? ? Au(s) + 4Cl?(aq) +0.93
MnO2(s) + 4H+ + e? ? Mn3+(aq) + 2H2O +0.95
[AuBr2]?(aq) + e? ? Au(s) + 2Br?(aq) +0.96
Br2(l) + 2e? ? 2Br?(aq) +1.07
Br2(aq) + 2e? ? 2Br?(aq) +1.09
IO3?(aq) + 5H+ + 4e? ? HIO(aq) + 2H2O +1.13
[AuCl2]?(aq) + e? ? Au(s) + 2Cl?(aq) +1.15
HSeO4?(aq) + 3H+ + 2e? ? H2SeO3(aq) + H2O +1.15
Ag2O(s) + 2H+ + 2e? ? 2Ag(s) +1.17
ClO3?(aq) + 2H+ + e? ? ClO2(g) + H2O +1.18
ClO2(g) + H+ + e? ? HClO2(aq) +1.19
2IO3?(aq) + 12H+ + 10e? ? I2(s) + 6H2O +1.20
ClO4?(aq) + 2H+ + 2e? ? ClO3?(aq) + H2O +1.20
O2(g) + 4H+ + 4e? ? 2H2O +1.23
MnO2(s) + 4H+ + 2e? ? Mn2+(aq) + 2H2O +1.23
Tl3+(aq) + 2e? ? Tl+(s) +1.25
Cl2(g) + 2e? ? 2Cl?(aq) +1.36
Cr2O72?(aq) + 14H+ + 6e? ? 2Cr3+(aq) + 7H2O +1.38
CoO2(s) + 4H+ + e? ? Co3+(aq) + 2H2O +1.42
2HIO(aq) + 2H+ + 2e? ? I2(s) + 2H2O +1.44
BrO3?(aq) + 5H+ + 4e? ? HBrO(aq) + 2H2O +1.45
2BrO3? + 12H+ + 10e? ? Br2(l) + 6H2O +1.48
2ClO3? + 12H+ + 10e? ? Cl2(g) + 6H2O +1.49
MnO4?(aq) + 8H+ + 5e? ? Mn2+(aq) + 4H2O +1.51
HO2? + H+ + e? ? H2O2(aq) +1.51
Au3+(aq) + 3e? ? Au(s) +1.52
NiO2(s) + 4H+ + 2e? ? Ni2+(aq) +1.59
2HClO(aq) + 2H+ + 2e? ? Cl2(g) + 2H2O +1.63
Ag2O3(s) + 6H+ + 4e? ? 2Ag+(aq) + 3H2O +1.67
HClO2(aq) + 2H+ + 2e? ? HClO(aq) + H2O +1.67
Pb4+(aq) + 2e? ? Pb2+(aq) +1.69
MnO4?(aq) + 4H+ + 3e? ? MnO2(s) + 2H2O +1.70
H2O2(aq) + 2H+ + 2e? ? 2H2O +1.76
AgO(s) + 2H+ + e? ? Ag+(aq) + H2O +1.77
Au+(aq) + e? ? Au(s) +1.83
BrO4?(aq) + 2H+ + 2e? ? BrO3?(aq) + H2O +1.85
Co3+(aq) + e? ? Co2+(aq) +1.92
Ag2+(aq) + e? ? Ag+(aq) +1.98
S2O82- + 2e- ? 2SO42- +2.07
HMnO4?(aq) + 3H+ + 2e? ? MnO2(s) + 2H2O +2.09
F2(g) + 2e? ? 2F?(aq) +2.87
F2(g) + H+ + e? ? HF2?(aq) +2.98
F2(g) + 2H+ + 2e? ? 2HF(aq) +3.05
if you're still not convinced , I shall try to elaborate more , reply.......
@seth
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[Post New]23 Feb 2007 16:27:42 IST
    Subject: Re:Cs or Li ???
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umang (229)

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Hey anurag !
you hav posted the entire table !!!!!!!
Ok , lets now cut it short . Just tell in short the final result .
Umang
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[Post New]23 Feb 2007 20:04:38 IST
    Subject: Re:Cs or Li ???
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Anurag.Seth (53)

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Hello Umang,
                     Final Result: Cs is more electropositive than Li.
 
 
 
Regarding Practicals,
                     I donot know whether I got the correct readings,
                 See my readings were:
Q1) Focal Length of concave lens 35.5cm
Q2) V=2V ; I0=2A
Q3)  = 0.44 (I donot remember well)
P=3.04ohm
 
What were your readings?
And Umang what Smriti Mam has sais is quite wondering,
 If there be 18electrons in an orbital the whole periodic table would contract to a single group.
 
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[Post New]27 Feb 2007 23:20:24 IST
    Subject: Re:Cs or Li ???
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Anurag.Seth (53)

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hello Umang,
                    I replied to your question a long ago?
                    Why haven't you responded thence?
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[Post New]28 Feb 2007 22:13:18 IST
    Subject: Re:Cs or Li ???
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umang (229)

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Hey anurag !
I was not online for the past few days .
and , what readings are u talking about ???
I am in class XI !!!!
be in touch !
BYE !!!!!!!!!
 
Umang
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[Post New]5 Mar 2007 16:17:35 IST
    Subject: Re:Cs or Li ???
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xantra88 (2)

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cs must be the ans as Li is smallerhan cs disabling it to give electrons readily than cs because of its small size
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[Post New]5 Mar 2007 19:17:10 IST
    Subject: Re:Cs or Li ???
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shine (262)

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hii umang !!!
just see that the we normally determine the I.E. considering the size of the atom & its screening effect of the inner electrons but in the gaseous state.
therefore accordingly
Cs > Li (size)
=>Cs <Li (IE)
 Cs is more electropositive then Li
now look
as far as sep is considered , it is for an ion in aqueous state
:: it is determined by
M(s) -> M(g)       SUBLIMATION ENTHALPY
M(g) -> M+(g)    IE(+ve)
M+(g) -> M+(aq) HYDRATION ENTHALPY(-ve)
 
THUS  apart from IE we also look at the hydration enthalpy which obviously is graeter for Li due to its smaller size
thus in total we get a higher sep for Li than Cs
 
bt only in solution
still due 2 verrrry low IE Cs is more electropositive than Li
  i hope u 've understood
if yes plzz reply & rate me.
there is no right way 2 do something wrong !!!!!!!!
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[Post New]5 Mar 2007 20:28:20 IST
    Subject: Re:Cs or Li ???
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umang (229)

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Hi shine !
Thanks for the solution . Yes , I hav completely understood ur solution . Here are my rates .
Umang
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[Post New]5 Mar 2007 22:28:20 IST
    Subject: Cs or Li ???
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shine (262)

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thanks a lot umang !!!!
there is no right way 2 do something wrong !!!!!!!!
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[Post New]5 Mar 2007 22:31:39 IST
    Subject: Re:Cs or Li ???
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umang (229)

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u r welcome !!!
Umang
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[Post New]6 Mar 2007 16:53:09 IST
    Subject: Re:Cs or Li ???
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arun.k.iit (7)

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its cesium


electro negativity
  Cesium--- 0.79
    Lithium ---- 0.98
ARUN

TRY,TRY,TRY TILL U SUCCEEEEEEEEEEEEEEEEEEED
YOU CAN DO WHATEVER U WANT,JUST TRY

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