Easy F.4 chem question

001 is wrong.
Copper(II) hydroxide is a soild, not aqueous, it can't dissove in h2o. Only potassium hydroxide, sodium hydroxide and calcium hydroxide(little soluble), this 3 metal hydroxide can dissove in h2o to dissociate to form OH- ion.

2010-06-12 22:59:31 補充：
Also, dig the pH paper into tested solution will let the dye on the paper go in to the solution.

it is not a good practice to dig the pH paper into the solution
1)the solution may be too corrosive to destroy the paper structure
2)If that is a coloured solution, it is difficult to observe the colour change of litmus paper


**Copper(II) hydroxide is a solid(pale blue gelatinous precipitate),which is
INSOLUBLE IN WATER
that means it cannot release any hydroxide ions to turn the red litmus peper
blue even with the presence of water

唔張pH paper dig落去solution度, 唔想污染左d solution。

至於點解Cu(OH)2唔turn moist red litmus blue ,
可能佢係moist~~ 或者可能佢係隻complex掛

It is not a good practive to dig the pH paper into the solution to be tested as the solution may be too acidic and alkaline that in case of any accidents, e.g. reactions between the solution and chemicals presented on the litmus paper, the reaction would be too vigorous and may not be under control. For safety reason, use a dropper to add a drop of solution to the litmus paper.

When Copper(II) hydroxide is added to a moist litmus paper, it turns from red to blue. The reason is that copper(II) hydroxide (aqueous) had mobile hydroxide ions that are basic/ alkaline.

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