Hydration reaction...請幫幫我呀﹗﹗

2011-01-01 6:15 am
以下reaction 是 Hydration reaction︰

CuSO4+ 5H2O--> CuSO4.5H2O
CoCl2 + 6 H2O-->CoCl2.6 H2O

此類 reaction 是chemical reaction嗎?
Please state reason(s).
更新1:

Re 己式庚辛: http://zh.wikipedia.org/zh-tw/%E6%B0%B4%E5%90%88 上面所寫的 "如果物質分子和整個水分子結合,生成水合物,其化學性質並不變更,並不是新物質"是錯誤的嗎? 因為webpage 說所有的inorganic compounds ge hydration reactions 它們(reactants)都只會與整個water molecule... So in that case, no new substance formed= no reaction?

更新2:

So, when wet cobalt chloride paper is heated in an oven and turn back to blue from pink, is it decomposition of water molecule, or simply vapourization of water?

回答 (1)

2011-01-01 7:11 am
✔ 最佳答案
yeah, they're chemical reactions. the products are different from the reactants -- new substances are formed.

for example, anhydrous CuSO4 is colorless, has density of 3.6g/cm^3, and can be heated to 650 degree before decomposition.
however, the pentahydrate is blue, has density of 2.3g/cm^3, and decompose at 110 degree.

the two species have different properties (especially chemical properties), so they're different compounds.
the reaction converts a substance into another new substance, so it's chemical reaction.


2011-01-01 04:15:54 補充:
... 唉, 說到那個層面的話, 就很難把反應分類的了...
問題像雞與雞蛋:
水合物是否新的物質?
如果水合的過程算是化學反應, 那水合物就是新的物質; 如果水合物是新的物質, 那水合的過程就算是化學反應.

我的看法是, 算化學反應, 因為兩者間最少有一個分別: 無水化合物能與水作水合反應, 而水合物則不會與水作水合反應.
離子/分子間的鏈結方式確是有本質上的改變;
以copper(II) sulphate 為例, 銅離子本來是被硫酸根離子包圍, 水合後改由水分子包圍.

很令人頭痛耶... 不過要考慮到這些的話, 其實是不是化學反應, 本身也不太重要了. (笑

2011-01-06 22:19:42 補充:
i'd say, Neither.
first, water molecules are NOT decomposed. they just escape from the crystal.

second, is that simple vaporization? i don't think so.
vaporization refers to change of state of free substance...

2011-01-06 22:24:51 補充:
對了, 我想起很重要的事!!

這些水合物的化學式是恆定的, 原子比例是恆定的,
即CuSO4 定會且只會有5個水 (且不論其他少見的水合物), 不會多也不會少.

如果水合作用是物理變化, 沒有新物質形成, 那即是造成混合物 ---- 而混合物的各物質比例是隨意的, 是不會有恆定的化學式或原子數比!

既然現在有恆定的化學式, 意味著不是物理過程生成的混合物,
而是由化學反應生成的"化合物" !!


收錄日期: 2021-04-19 23:50:18
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20101231000051KK01509

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