Chem

emmacherry

原帖由 Zend 於 20-4-2008 19:22 發表

你可以當成CuSO4.5H2O 有某個chemical energy
CuSO4 有另一個

CuSO4.5H2O->CuSO4 唔會自己發生, 要energy 去做decomposition
所以CuSO4 同佢product 的total 能量係多左

當你加番水, 做番form water of cr ...

但係加左水
CuSO4會form water of crystallization 咩?
佢唔係會dissovle咩??

Zend

原帖由 emmacherry 於 20-4-2008 11:26 發表

但係加左水
CuSO4會form water of crystallization 咩?
佢唔係會dissovle咩??

以CaCl2(吸濕elephant) 為例
佢吸左水係先變water of crystallization, 過多先會溶埋成CaCl2(aq)
其實water of crystallization 只不過係water molecules 同個crystal 入面d cation, anion 有attraction ja ma.

你再加熱, 整走哂d 水就anhydrous

dissolve, 我解釋左, 即使佢係發生, 佢overall 都係exothermic

octopus001

原帖由 emmacherry 於 20-4-2008 11:26 發表

但係加左水
CuSO4會form water of crystallization 咩?
佢唔係會dissovle咩??

照你咁講 ...
你會點做crystallization?

Zend

Compound: CuSO4(s)
dH0solution/kj/mol: -66.5

Compound: CuSO4.5H2O(s)
dH0solution/kj/mol: +11.7"

如果1 mol 的CuSO4 溶係infinitely amount of water(唔好問點解, 定義)
佢會release 66.5KJ mol^-1 的能量(-ve = exothermic)
如果係個water of crystallization溶, 佢係吸+11.7 KJ mol^-1 的熱
因此, overall, 我唔理你係變CuSO4.5H2O 又好, 溶左係水變成CuSO4(aq)(真係看water 多定少)... 都係exothermic

anyway, 此等題目應該唔會係new syllabus 出現

octopus001

原帖由 Zend 於 20-4-2008 11:49 發表
Compound: CuSO4(s)
dH0solution/kj/mol: -66.5

Compound: CuSO4.5H2O(s)
dH0solution/kj/mol: +11.7"

如果1 mol 的CuSO4 溶係infinitely amount of water(唔好問點解, 定義)
佢會release 66.5KJ mol^-1 的 ...

我想問...
如果考果d ... 佢比d我唔識的reaction..
咁點知佢點先係exo 定 endo ....reaction?

piyopiyo

是否這樣...
CuSO4 . 5H2O,,,要decompose就要加熱,個hydrated salt就吸左d energy去爆個bond,,,this is an endothermic reaction [[tk_02]]
調番轉將CuSO4 變番hydrated salt要放熱[[tk_02]]  by conservation of energy[[tk_21]]

emmacherry

原帖由 Zend 於 20-4-2008 19:49 發表
Compound: CuSO4(s)
dH0solution/kj/mol: -66.5

Compound: CuSO4.5H2O(s)
dH0solution/kj/mol: +11.7"

如果1 mol 的CuSO4 溶係infinitely amount of water(唔好問點解, 定義)
佢會release 66.5KJ mol^-1 的 ...

ok thanks
但係我最後都想問
到底我地加水落copper(II) sulphate
佢係會溶定form water of crystallization ??
因為我睇書
要form water of crystallization 係要經過一個crystallization o既程序
唔係直接dissolve 就有的

Zend

原帖由 octopus001 於 20-4-2008 11:57 發表






我想問...
如果考果d ... 佢比d我唔識的reaction..
咁點知佢點先係exo 定 endo ....reaction?

第一佢唔會考
第二, 放得熱主要有四類

neutralization
precipitation
combustion (usually 係, 包括用oxidizing agent 好似O2, Cl2,F2 )
Redox, 可行果d 一般直接mix 都會放熱, cell 只係將佢(chemical energy)變成electrical energy的東西..

仲有幾隻我都唔記得 XD

Zend

原帖由 emmacherry 於 20-4-2008 12:00 發表

ok thanks
但係我最後都想問
到底我地加水落copper(II) sulphate
佢係會溶定form water of crystallization ??
因為我睇書
要form water of crystallization 係要經過一個crystallization o既程序
唔係直接d ...

你可以這樣想, 就算佢form左solution,你加熱番佢都會出到water of crystallization
比個counter-example你

http://en.wikipedia.org/wiki/CaCl2

一般water of crystallization都係crystallization of solution出, 但我唔可以generalized 所有都係
特別係Na2CO3, MgSO4, CaCl2 這些吸水常客

emmacherry

原帖由 Zend 於 20-4-2008 20:01 發表

第一佢唔會考
第二, 放得熱主要有四類

neutralization
precipitation
combustion (usually 係, 包括用oxidizing agent 好似O2, Cl2,F2 )
Redox, 可行果d 一般直接mix 都會放熱, cell 只係將佢(chemical ene ...

仲有係
CuSO4+ 5H2O-----> CuSO4.5H2O
同埋
CaO + H2O----->Ca(OH)2