FAQ ; Electrolysis

SPM Frequently Ask Question :

TOPIC : ELECTROCHEMISTRY 

     ELECTROLYTIC CELL

Structure question : You should study on these

• 1.       Energy changes in cell

• 2.       Which electrode will act as anode/ cathode

• 3.       Show the direction of electron flow at connecting wire

• 4.       State the observation at electrode

• 5.       State the colour change of electrolyte

• 6.       State all the  ions presence in electrolyte

• 7.       The meaning of cation and anion

• 8.       State selective ions discharged at anode and cathode

• 9.       Write half equation at anode and cathode

• 10.   State/name the products at cathode and anode

             Eg :

2         Figure 2 shows the apparatus set-up used to electrolyse Copper(II) sulphate  0.001 mol dm^-3 using carbon electrodes.

Rajah 2 menunjukkan susunan radas yang digunakan untuk mengkaji elektrolisis larutan kuprum(II) sulfat  0.001 mol dm^-3  menggunakan elektrod karbon.

 

              (a)          What is meant by the term cation ?

Apakah yang dimaksudkan dengan kation ?

                                Positively charged ion (Ion yang bercas positif)

                                                                                                                                                             [ 1 mark]

                (b)          What is the energy change that occurs in the cell?

Apakah perubahan tenaga yang berlaku dalam sel itu?

Electrical Energy to Chemical Energy                                                                  [1 mark]

.

                (c)     State which electrode  acts as the

Nyatakan elektrod yang mana bertindak sebagai

Cathode :

Electrode carbon Y

Anode :

Electrode carbon X

*refer to dry cell terminal

                                                                                                                                                                [ 1 markah]

(d)          Write the formulae of all ions present in aqueous Copper(II) sulphate solution

Tuliskan formula bagi semua anion yang terdapat dalam larutan kuprum(II)  sulfat.

                             

                           SO₄^2- dan OH^-                                                                                                   [ 1 markah]

             (e)         State the selective ion discharged at Anode?

Nyatakan ion yang terpilih dinyahcaskan di anod?

                           

                          OH^-            

* tiga faktor perlu diambilkira sebelum memilih ion yang mana akan dinyahcaskan (samada di katod ataupun di anod)

(f)         Write the half equation of the reaction at the

Tuliskan persamaan setengah bagi tindak balas di

Anode :

                                4OH^-     →     2 H₂O        +       O₂    +  4e

[1 mark]

Cathode :

2H⁺   +    2e    →  H₂                                                                                               [1 mark]

                  (g)          What can be observed at Cathode?

                                  Apa yang dapat diperhatikan di katod?

                                                

                                    Colourless bubble gas is formed

                                    *mesti nyatakan warna gas/ larutan

                   (h)          Name the products at cathode

                                  Namakan hasil di katod

                                               

                                      Hydrogen gas

*tuliskan nama bahan tersebut.  JANGAN tuliskan formula bahan (lihat kehendak soalan)

       (i)            Draw arrows indicating the flow of electrons in Diagram 2.

                     Lukis anak panah yang menunjukkan pergerakan elektron pada Rajah 2.

                                As shown as in diagrams