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

FAQ ; Chemical cell

SPM Frequently Ask Question :

TOPIC : ELECTROCHEMISTRY

CHEMICAL CELL

Structure question : You should study  these

• 1.       The function of  Salt bridge  and Porous Pot

• 2.       Energy changes in cell

• 3.       State/write all the  ions presence in electrolyte

• 4.       Which electrode will act as anode/ cathode or negative terminal/ positive terminal ( must based on Electrochemical series)

• 5.       Write half equation at anode and cathode

• 6.       State the colour change of electrolyte

• 7.       State the observation at electrode

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

 

Eg :

 

         Diagram 3 shows the set-up of apparatus of a chemical cell.

Rajah 3 menunjukkan susunan radas sebuah sel kimia.

(a)                What is the function of the porous pot?

Apakah fungsi pasu berliang?

to allow the movement/flow of the ions.                                                            [1 mark]

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

Apakah perubahan tenaga yang berlaku dalam sel itu?

Chemical Energy to electrical Energy                                                                  [1 mark]

(c)                Write the formula all ions present in the Copper(II) sulphate solution?

Tuliskan formula semua ion-ion yang terdapat dalam larutan kuprum(II) sulfat?

Cu²⁺ ,  SO₄^2- , H⁺ and OH^-                                                                 [1 mark]

(a)                State which metal plate acts as the

Nyatakan kepingan yang mana bertindak sebagai

negative terminal :

terminal negatif :

Zinc Plate *

positive terminal :

terminal positif :

                                Copper Plate   *

* mesti merujuk siri elektrokimia ; Logam yang berada di atas dalam siri elektrokimia bertindak sebagai terminal negative, manakala logam yang terletak di bawah bertindak sebagai terminal positif

 [1 mark]

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

Tuliskan persamaan setengah bagi tindak balas di

negative terminal :

terminal negatif :

                                Zn     →      Zn²⁺        +        2e

[1 mark]

positive terminal :

terminal positif :

Cu²⁺       +       2e     →    Cu

[1 mark]

(e)          What is the colour change of the copper (II) sulphate solution? Explain your answer.

Apakah perubahan warna yang berlaku kepada larutan kuprum(II) sulfat? Terangkan jawapan anda.

                         *Blue to colourless / becomes fade / paler

The number of copper(II) ions decrease //The concentration of copper(II) ions decrease

[2 marks]

* copper(II) sulphate colour is blue  - you must remember this

(f)           What will be observed at copper plate?

Apa yang diperhatikan pada kepingan kuprum ?

                plate becomes thicker / kepingan kuprum menebal

(g)          Draw arrows indicating the flow of electrons in Diagram 3.

                Lukis anak panah yang menunjukkan pergerakan elektron pada Rajah 3.

                As shown as in diagrams

[1 mark]