Page 148 - Nilam_Publication_module_Chemistry_Form.pdf

MODULE • Chemistry Form 4

2 The following is the steps in the preparation of dry copper(II) sulphate crystals.
Berikut adalah langkah-langkah dalam penyediaan hablur garam kuprum(II) sulfat kering.

Step I: Copper(II) oxide powder is added a little at a time with constant stirring to the heated 50 cm of
3
1 mol dm sulphuric acid until some of it no longer dissolve.
–3
3
Langkah I: Serbuk kuprum(II) oksida ditambahkan, sedikit demi sedikit sambil dikacau ke dalam 50 cm asid sulfurik
-3
1 mol dm yang dipanaskan sehingga serbuk itu tidak boleh larut lagi.
Step II: The mixture is f ltered.
Langkah II: Campuran dituras.

Step III: The f ltrate is poured into an evaporating dish and heated to evaporate the solution until one
third of its original.
Langkah III: Hasil turasan dipanaskan di dalam mangkuk penyejat sehingga isi padunya menjadi satu pertiga
daripada isi padu asal.

Step IV: The salt solution is allowed to cool at room temperature for the crystallisation to take place.
Langkah IV: Hasil turasan itu dibiarkan sejuk ke suhu bilik sehingga penghabluran berlaku.

Step V: The crystals formed are f ltered and dried by pressing them between f lter papers.
Langkah V: Hablur yang terbentuk dituraskan dan dikeringkan dengan menekan antara kertas turas.

(a) (i) State two observations during Step I.
Nyatakan dua pemerhatian pada Langkah I.
– Black solid dissolve
– Colourless solution turns black

(ii) Write a balance chemical equation for the reaction that occur in Step I.
Tuliskan persamaan kimia seimbang bagi tindak balas yang berlaku dalam Langkah I.
CuO + H 2 SO 4 CuSO 4 +H 2 O
(iii) State the type of reaction in the preparation of the salts.
Nyatakan jenis tindak balas yang berlaku dalam penyediaan garam.
Neutralisation

(b) Why is copper(II) oxide powder added until some of it no longer dissolve in Step I?
Mengapakah serbuk kuprum(II) oksida ditambah pada larutan tersebut sehingga ia tidak boleh melarut lagi dalam Langkah I?
To make sure that all sulphuric acid has reacted.

(c) What is the purpose of heating in Step III?
Apakah tujuan pemanasan dalam Langkah III?
To evaporate the water and copper(II) sulphate solution becomes saturated

(d) What is the colour of copper(II) sulphate?
Apakah warna kuprum(II) sulfat?
Blue

(e) What is the purpose of filtration in
Apakah tujuan penurasan dalam
(i) Step II? / Langkah II?
– To remove the excess copper(II) oxide.
– To obtain copper(II) sulphate solution as a filtrate
(ii) Step V? / Langkah V?
To obtain copper(II) sulphate crystals as a residue.

146
Nilam Publication Sdn. Bhd.

07-Chem F4 (3p).indd 146 12/9/2011 5:55:22 PM