Assignment 5 Simulation Modelling

7/31/2019 Assignment 5 Simulation Modelling

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SIMULATION [SKP6024 - Technology And Innovation In Teaching And Learning Chemistry]

SKP 6024

TECHNOLOGY AND INNOVATION IN TEACHING

AND LEARNING CHEMISTRY

GROUP ASSIGNMENT:


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ELECTROLYSIS

Teachers Guide / Chemistry Form 4 / Simulation

SCIENTIFIC CONCEPT

Conductor

A conductor is a substance which conducts electricity but is not chemically changed during theconduction.

InsulatorsA non-conductor is a substance which does not allow the passage of electricity. Sometimes these

non-conductors are used to protect something from electricity. They are then called insulators.

Electrolytes
http://wiki.one-school.net/index.php/Image:Electrolyte.png


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Factor Affecting Electrolysis

There are 3 factors that may influence the selective discharge of ions during the electrolysisof an aqueous solution.

When more than one type of ions move towards the electrode during electrolysis, only onetype of ion is selected to be discharged.

Selective discharge only occur in aqueous solution because it usually has more than one typeof ions attracted to the anode or cathode.

The selection of ion for discharge depends on three factors :i) The position of ions in the Electrochemical Series (normally in dilute solution and

inert electrodes are used)

ii) The concentration of electrolyte / ions (normally in concentrated solution andinert electrodes are used)

iii) The types of electrode (when active metal electrode is used)

(I) The position of ions in the Electrochemical Series

When electricity is conducted in dilute solution used inert electrodes, the cations oranions in the lower position in the Electrochemical Series will be selectively discharged.

Electrochemical Series

Cation Anion


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The chart above lists the ions in order of difficulty of discharge The ions at the top of the list is more difficult to be discharged, but as we go down the

table, their become easier to be discharged. For example, Cu+

easier to be discharged

compare with Ag+

and OH-is easier to be discharged compare with I

-.

This series is called Electrochemical series The lower the ion in the electrochemical series, the easier the ion to be discharged during

electrolysis.

Example :

Electrolysis of 0.1 mol dm-3

sulphuric acid, using carbon electrodes.

Apparatus set-up :

carbon electrodes


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Name of the products at the

anode and cathodeOxygen Hydrogen

Observations Gas bubbles are released Gas bubbles are released

Confirmatory test

[methodandobservations of

the test]

Insert glowing wooden splinter

into the test tube

When the ligthed wooden

splinter is placednear the mouth

of the test tube

Glowing wooden splinter is

lighted up

A pop sound is produced

(II) Concentration of electrolyte

When electrolysis is carried out using inert electrodes and concentrated solutions, ions that aremore concentrated will be selected to discharge, but this is only true for halide ions; which are

Cl-, Br

-and I

-.

Example:

Electrolysis of :

Set I : 0.001 mol dm-3

hydrochoric acid, HCl(aq)

Set II : 2.0mol dm-3

hydrochoric acid, HCl(aq)


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The electrolyte ionisation

equation

HCI H+

+ CI-

H2O H

+

+ OH

-

Ions exist in electrolyteH

+, CI

-, OH-

Set I : 0.001 mol dm-3diluteHCl Set II : 2.0 mol dm

-3concentratedHCl

The ions that are move to

the cathodeH

+ H

+

Ions that are selectively

discharge H+

H+

Discharge equation at the

Cathode

2H+ + 2e H2 2H+ + 2e H2

Name of theproduct at

the CathodeHydrogen gas Hydrogen gas

The ions that move to the

AnodeOH

- CI-

OH- CI

-

Selective ion OH

-

CI

-


Anode

4OH- 2H2O + O2 + 4e 2CI-

CI2 + 2e

Name of the product at

the AnodeOxygen gas Chlorine gas

Observation Gas bubbles are released Greenish yellow gas is released

Confirmatory test for

product form at anode*.[methodandobservation

f th t t ]

Insert glowing wooden splinter

into the test tube

A damp blue litmus paper placed near

the mouth of the test tube

Glowing wooden splinter is

li ht d

The gas changed the damp blue litmus

t d d th bl h d it


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(III) Types of electrode

There are two types of electrode :

Inert electrodeAn electrode that acts as a conductor of current only and does not undergoany chemical

changes.Normally are made ofcarbonorplatinum. These electrodes do not participate in

an electrolysis but merely provide a surface for the release of electrons.

Non-inert/ active electrodeAn electrode that not only acts as a conductor of current but also undergoes chemical

changes. During the electrolysis, the metal anode will corrode while the reaction at the

cathode is similar to the reaction at carbon electrode. Consist of metal anodes such as

copper, silver and nickel.

Example :

Set I : Electrolysis of 0.02 mol dm-3

silver nitrate solution using carbon electrodes

Set II : Electrolysis of 0.02 mol dm-3

silver nitrate solution using silver electrodes

Apparatus set-up :

Set I : Carbon electrodes Set II : Silver electrodes


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Set I : Carbon electrodes Set II : Silver electrodes


cathodeAg

+ H+ Ag

+ H+


cathodeAg+ + e Ag Ag+ + e Ag


the cathodeSilver solid Silver solid


anodeOH- NO2-3 OH

- NO2-3


anode

4OH- 2H2O + O2 + 4e Ag Ag+ + e


the anodeOxygen Silver solid

Observations

at the

Cathode Grey shiny solid deposited Grey shiny solid deposited

Anode Gas bubbles are released Anode becomes thinner

UNIQUE FEATURE OF THIS ACTIVITY


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ENGAGING

Figure 1

1. What do you understand about Figure 1 diagram?2. Give 3 factors that can affect light in the bulb3. What the different between electrolyte and non electrolyte?
http://wiki.one-school.net/index.php/Image:Electrolyte.png


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EMPOWERING

1. Electrolysis is the dissociation of an electrolyte into ions at the electrodes by the passage of

electric current.

2. In electrolysis, the circuit must contain with:

a) electrode

b) Aqueous solution

c) Electric current

d) Wires

3. Log on the web side and observe the animation to answer the question.

http://www.tutorvista.com/content/chemistry/chemistry-ii/electrolysis/electrolysis-animation.php
http://www.tutorvista.com/content/chemistry/chemistry-ii/electrolysis/electrolysis-animation.phphttp://www.tutorvista.com/content/chemistry/chemistry-ii/electrolysis/electrolysis-animation.phphttp://www.tutorvista.com/content/chemistry/chemistry-ii/electrolysis/electrolysis-animation.php


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Electrolysis is the dissociation of an electrolyte into ions at the electrodes by the passage of electric

current.


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This diagram show that when we use electrode and have electric current, the ions move. We used copper

electrode and copper sulfate solution.


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Question

1. What is the meaning of conductor?2. What do you understand about electrochemical series?3. Give three factor that affect electrolysis.

Answer

1. A conductor is a substance which conducts electricity but is not chemically changedduring the conduction.

2.
http://wiki.one-school.net/index.php/Image:ElectrochemicalSeries.png


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ENHANCE

Application Of Electrolysis In Daily Life

The storage battery

A fully charged lead storage cell

A widely used lead acid battery, the storage battery was invented in 1859 by the French physicist

Gaston Plant. Reversing the chemical reaction can recharge this battery. It consists of three or six

cells, which are connected in a series. So the electricity generated by it is very strong.

Because of this, it has found wide usage in automobiles, trucks and other vehicles. The catch here

is that this type of battery runs down very quickly. However its ability to recharge itself while ini h d h h dl d i h i f i id d


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[14]

The table below shows three electrolytic cells with different electrolytes and different electrodes. You are required to answer each section by

writing your answer in the spaces provided.

1. In the diagrams, label the cathode with thesymbol and theanode with the symbol +.

2. Show the direction of the flow of theelectrons with arrowheads, >

3. Write the formula of all ions in theelectrolyte.

4. Write the formula of ions which areattracted to the cathode.

Underline the formula of ion which isselectively discharged.

5. Write the half equation to represent thereaction at the cathode.

6. What will you observe at the cathode?

7. Write the formula of ions which areattracted to the anode.

Underline the formula of ion which is

selectively discharged.8. Write the half equation to represent the

reaction at the anode.

9. What will you observe at the anode?


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[15]

Anwers :

1

2

3Na+, Cl

, H+ , OH

Na

+, Cl, H+ , OH

Cu

2+, SO42, H+, OH

4Na+, H+ Na+, H+ Cu2+, H+

52H

++ 2e H2 2H

++ 2e H2 Cu

++ 2e Cu

6 Gas bubbles are formed Gas bubbles are formedBrown solid deposited on the cathode

7Cl

, OH

ions Cl

, OH

ions SO4

2, OH

8

2Cl

Cl2 + 2e 4OH

2H2O + O2 + 4e Cu Cu2+

+ 2e

9Gas bubbles are formed Gas bubbles are formed Copper plate becomes thinner

Assignment 5 Simulation Modelling

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