一條CHEM問題..唔該幫下手..

2009-04-11 6:49 am
On heating, blue copper(II) sulphate crystals gradually change to a white powder. Which of the following statements are correct?

(1)Heat would be liberated if water is added to the white powder.

(2)On further heating, the white powder would turn reddish-brown.

(3)A chemical change occurs during the heating of the blue crystals.

答案係 (1)同 (3) 可唔可以解釋一下點解 (1), (3)岩..(2)錯既?

回答 (1)

2009-04-11 8:03 pm
✔ 最佳答案
Statement 1: T
The white powder is anhydrous copper(II) sulphate, as heat removes the water of crystallization of hydrated copper(II) sulphate.
Addition of water to anhydrous copper(II) sulphate is an exothermic reaction. Therefore heat is liberated.
Statement 2: F
Copper metal( reddish - brown in colour ) cannot be obtained by heating its ore( CuSO4 ) alone.
Statement 3: T
Heating the blue crystals changes the chemical form of them, i.e. from hydrated form to anhydrous form. Hence it is a chemical change.
Therefore, (1) and (3) are correct.
參考: My Chem Knowledge


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