preparation of salt

2009-06-14 4:14 am

Question : prepare pure dry CuSO4．5H2O
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Answer :
1)Some copper(II) oxide is added to the dilute sulphuric acid and stir well.
2)More copper(II) oxide is added until it is in excess.
3)The excess copper(II) oxide is filtered off from the soution.
4)The filtrate is heated until crystals just started to form and then left to cool.
5)The crystals are collected and washed with small amount of distilled water.
6)Then the crystals are dried without heating with filter paper.
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5) 點解要洗 ?
6) 點解唔可以 heat佢.. ? 擺入 oven 唔係仲乾過用 filter paper 咩 ?

回答 (2)

老爺子

2009-06-14 4:50 am

✔ 最佳答案

5.
This is to remove the solution which is stuck on the copper(II) sulphate crystals.

6.
If the crystals are heated, the water of crystallization would be removed at high temperature.
CuSO4•5H2O(s) → CuSO4(s) + 5H2O(g)
=

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冷風

2009-06-14 7:54 am

用OVEN需時較長(慢慢等crystals自己乾)

用filter paper則比較簡易方便, 短時間弄乾crystals

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