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MODULE • Chemistry Form 4

Electrical current produced is detected by the galvanometer
(Chemical energy Electrical energy)
Arus elektrik terhasil dikesan oleh galvanometer G
(Tenaga kimia Tenaga elektrik)
Negative terminal / Terminal negatif : Positive terminal / Terminal positif :
• More electropositive metal. _ + • Less electropositive metal.
Logam lebih elektropositif. Logam kurang elektropositif.
• Metal atom will release electrons that will • The electrons that flow from the external
flow through the external circuit. Metal atom circuit are received by the positive ion in
becomes metal ion (becomes thinner). the electrolyte through this terminal.
Atom logam akan melepaskan elektron yang akan Elektron yang akan mengalir dari litar luar diterima
mengalir di litar luar. Atom logam menjadi ion logam oleh ion positif dalam elektrolit melalui terminal ini.
(semakin nipis).
6 Example of simple voltaic cell / Contoh voltan sel ringkas:

V

Copper Magnesium
Kuprum Magnesium
Copper(II) sulphate solution
Larutan kuprum(II) sulfat

(a) Magnesium electrode is a negative terminal because magnesium is more electropositive than copper :
Elektrod magnesium adalah terminal negatif kerana magnesium lebih elektropositif daripada kuprum :
2+
– Magnesium atom releases electrons to form magnesium ion, Mg .
Atom magnesium melepaskan elektron untuk membentuk ion magnesium, Mg .
2+
2+
– Half equation / Persamaan setengah : Mg Mg + 2e .
– Magnesium electrode becomes thinner / Elektrod magnesium menjadi nipis .
– Electron flows through external circuit to the copper electrode.
Elektron mengalir melalui litar luar ke elektrod kuprum .

(b) Copper electrode is a positive terminal because copper is less electropositive than magnesium :
Elektrod kuprum adalah terminal positif kerana kuprum kurang elektropositif daripada magnesium :
– Electrons from magnesium flow through external circuit to copper electrode.
Elektron dari magnesium mengalir melalui litar luar ke elektrod kuprum.
– Copper(II) ion in the electrolyte receives electron to form copper atom.
Ion kuprum(II) dalam elektrolit menerima elektron untuk membentuk atom kuprum.
+
– Half equation / Persamaan setengah : Cu + 2e Cu .
– Brown solid is deposited on the surface of copper electrode.
Pepejal perang terenap di permukaan elektrod kuprum.

(c) The concentration of copper(II) sulphate decreases because copper(II) ions discharged to copper atom at the
positive terminal. The intensity of blue colour of copper(II) sulphate decreases.
Kepekatan larutan kuprum(II) sulfat berkurang kerana ion kuprum(II) dinyahcaskan kepada atom kuprum. Keamatan
warna biru larutan kuprum(II) sulfat berkurang.
(d) If the magnesium metal is replaced with a zinc metal, the voltage reading decreases because zinc is nearer to
copper in the electrochemical series.
Jika logam magnesium digantikan dengan logam zink, bacaan voltan akan berkurang kerana zink lebih dekat dengan kuprum
dalam siri elektrokimia.

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