[AL] Lattice enthalpy ~help

octopus001

A person made the following ermark:
"When cmpared woth CaO(s), MgO(s) has a more -ve lattive enthalpy and is therefore more stable from the point of energetics"
Do you agree? Explain.

piyopiyo

No
唔同element點比較ar[[tk_22]]
打個比喻
2個人跑步,阿A跑到A點就停la,阿B過左A點再跑多10米
阿B好似跑得多過A,但原來2個人起跑果點都唔同,所以其實係唔知邊個跑得遠d[[tk_36]]

[ 本帖最後由 piyopiyo 於 19-11-2008 20:11 編輯 ]

octopus001

明解了.....

[ 本帖最後由 octopus001 於 19-11-2008 13:08 編輯 ]

Zend

energy change 唔反映個species 係stable d 定less stable d

L.K.

咁點睇佢 stable d 定less stable
我前日做功課用左  Lattice enthalpy黎搵邊個stable d.....[[tk_35]]

Puppet

Ca2+(g) + O2-(g) --> CaO(s) ΔH < 0 means CaO(s) is energetically more stable than [Ca2+(g) + O2-(g)]

Lattice energy: used to compare ionic bond strength
Stability: need to consider the IE, EA, etc, therefore, the enthalpy change of formation.

j32738

呢題我F.6下學期做過,最近又做過

No
係因為stable or not睇enthalpy change of formation(c.f個element)

當然你要解釋點解上半句岩

Zend

enthalpy change of formation of one stuff > other stuff (different chemicals)
then u can say 大d magnitude = more stable??

我地定S.E.C of formation of element in standard state =0 KJ mol^-1
唔通代表左O2 ge "energy" 係一樣於"C(graphite)" ge energy?
我地只能夠用佢比較同一種constituents ge compounds ja bor
e.g. MgCl, MgCl2, MgCl3 Mg2Cl2...
CaO 同MgO 係不能直接比較

j32738

所以要比較from Ca去CaO 既enthalpy Change
同Mg 去MgO既enthalpy change

piyopiyo

原帖由 j32738 於 22-11-2008 13:11 發表
所以要比較from Ca去CaO 既enthalpy Change
同Mg 去MgO既enthalpy change

但係都比較唔到CaO定MgO邊個stable d gor wor[[tk_36]]