electrochemistry.docx

8/12/2019 electrochemistry.docx

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1. Apparatus and Reagent1. Test tube and test tube rack2. Burner3. Filter paper4. Graduated Cylinder5. Beaker Glass6. Dropping pipette7. Funnel8. Electrode Cu plate9. Salt bridge10.Carbon electrode11.pH meter12.Tube with U type13.GV AC current source14.Al, Cu, Fe, Mg, Pb, Zn

metal

15.Solution of Pb(NO3)20.1 M16.Solution of Zn(NO3)20.1 M17.Solution of 0.1 M AgNO318.Solution of 0.1 M NaNO319.Solution of 6 M HCl20.Solution of 0.1 M FeCl321.Solution of 0.1 M KI22.Solution of 0.25 M KI23.Solution of H2SO424.Solution of 0.1 M H2O225.Solution of starch26.Solution of CuSO427.Solution of ZnSO428.Solution of SnCl20.1 M29.PP indicator


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2. Observation Dataa.Redox Reaction

1) Reaction of metal and metal nitrate solutionMetal Pb(NO3)2 Zn(NO3)2 NaNO3 AgNO3

AlThere are

not reaction

A few of

precipitate

There are

not reaction

There are not

reaction

CuThere are

not reaction

There are

not reaction

There are

not reaction

The color of

Cu change

into black

FeThere are

not reaction

There are

not reaction

There are

not reaction

There are not

reaction

Table 1. Reaction of metal and metal nitrat solution

2) Reaction of metal and HCl solutionMetal Observation

Cu No reaction

Fe No reaction

Mg Bubbling, fast, and heat

Zn Bubbling, slowPb No reaction

Table 2. Reaction of metal and HCl solution


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3) H2O2+ H2SO4+ KI + starch :there is percipitate disperse in there, the color is yellow-red-brown.

The reaction :

Oxidation

Reduction

4) FeCl3+ H2SO4 + KI heated + starch :There is black colored precipitate and the solution has yellow

colored.

The reaction :

Oxidation

Reduction

5) Zn + CuSO4:Cu becomes powder

The reaction :

A (-) : Zn(s) Zn2+

+ 2e

C (+) : Cu2+ + 2e Cu(s)

Zn(s)+ Cu2+ Zn2++ Cu(s)

Cu + ZnSO4:

Observation : there are not occur reaction

Cu + ZnSO4

OHSOKISOHIKOH

1

242

0

242

1

2

2

2 2

eHSOFeHClSOKISOHIKClFe

4

2

42

0

242

1

3

3

362


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b.Electrolysis of KI solutionObservation Solution on Anode Solution on Cathode

Visual/Change Yellow Colorless + gas bubbles

Color

+ starch solution :

Green, and any percipitate

+CHCl3

Orange layer at the bottom

+ PP solution :

Pink colored

+ FeCL3 :

Red colored

Smell hospital smelt No smell

Reaction 2I-(aq)I2(g)+ 2e 2H2O9aq)+ 2e 2OH(aq)+H2(g)

Table 3. Electrolysis of KI solution

c. Electrolysis of CuSO4Observation Solution on Anode Solution on Cathode

Using C electrodeBubbling Nobubbling

Occurred change

reaction

+ starch : no change

color

+CHCl3: white

separated in the

solution

+PP : no change color

+FeCl3 : bright green

Reaction 2H2O(l) 4H++O2(g)+4e Cu

2++2e Cu(s)

Table 4. Electrolysis of CuSO4


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The reaction is:

Fe (s)+ Pb(NO3)2(aq) Fe(NO3)2(aq) + Pb (s)

Fe (s)+ Zn(NO3)2(aq)

Fe (s)+ AgNO3(aq) Fe(NO3)2(aq) + 2Ag(s)

Fe (s)+ NaNO3(aq)

2) Reaction of metal and HCl solutionIn this experiment, we insert some metals like Cu, Fe, Mg, Zn and

Pb into HCl solution. From the experiment, there are two metals that

cannot react with HCl solution. They are Cu metal and Pb metal. Cu

metal cannot react with HCl solution because Cu metal position in volta

series is Hs right. And for Pb metal, based on the theory, Pb metal can

react with HCl solution. But in this experiment Pb could not. Perhaps in

the surface of Pb metal, there is a few bubbles but we cannot see it.

The reaction is:

Fe (s)+ 2HCl (aq) FeCl2(aq) + H2(g)

Mg (s)+ 2HCl (aq) MgCl2 + H2(g)

Pb (s)+ 2HCl (aq) PbCl2(aq) + H2(g)

Cu (s)+ 2HCl (aq)

Zn (s)+ 2HCl (aq) ZnCl2(aq) + H2(g)

3) H2O2+ H2SO4+ KI + starch :This reaction is done to shown happened of redox reaction. In the

experiment, we react H2O2 solution with H2SO4 solution, KI solution,

and starch solution. The color of solution is yellow-red-brown. In thiscase, oxygen happens reduction and Iodium happens oxidation. The

reaction is :

OHSOKISOHIKOH24224222

2


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4) FeCl3+ H2SO4 + KI heated + starch :This experiment also shown redox reaction. In this case, FeCl3 is

reacted with H2SO4 to form acid solution and then react with KI

solution. Because this reaction cannot react in room temperature, so the

solution is heating. After heating the solution becomes yellow and there

is black colored precipitate. The reaction is :

5) Zn + CuSO4:When Zn metal insert into CuSO4 solution, Zn can react with

CuSO4. There are some bubbles and Cu becomes black. But, when Cu

insert into ZnSO4 there are no reaction. It is because E of Zn metal is

fewer than E of Cu metal. The reaction is:

Zn(s)+ CuSO4 (aq) ZnSO4 (aq) + Cu(s)

Cu(s) + ZnSO4 (aq)

b.Electrolysis of KI solutionOn next experiment, we use electrode C. after 15 minutes, there are

many changes. In anode, happens leach electrode and the color becomes

yellow. In the catode there are some bubbles and colourless. And then we

take some solution of anode and add starch solution and CHCl3 solution.

When we add CHCl3 solution, the color becomes orange and when we add

starch solution, it becomes green.

On the other hand, we take cathode solution and we add PP and FeCl3

solution. When we add PP solution it becomes pink and when add FeCl3solution it becomes red. The reaction is:

KI(aq) K+

(aq)+ I-(aq)

Cathode (-) :2H2O(l)+ 2e 2OH-(aq)+ H2(g)

Anode (+) :2I-(aq) I2(s) + 2e

Reaction cell :2H2O(l)+ 2I-(aq) I2(s)+ 2OH

-(aq) + H2(g)

eHSOFeHClSOKISOHIKClFe

4422423 362


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c. Electrolysis CuSO4(aq)with electrode CBefore reaction the color is blue. After reaction, in anode there ar e some

burble. But in cathode there are not burble but formed precipitate of Cu.

The burble is from H2O molecule. The reaction is:

CuSO4(aq) Cu2+

(aq)+ SO42-

(aq)

Cathode (-) :Cu2+

(aq)+ 2e Cu(s) |x2| 2Cu2+

(aq)+ 4e 2Cu(s)

Anode (+) :2H2O(l) 4H+

(aq) + O2(g)+ 4e

Cell reaction : 2Cu2+(aq)+ 2H2O(l) 2Cu(s)+ 4H+

(aq)+ O2(g)

4. Conclussion and SuggestionConclusion :

1. Redox reactions are characterized by changes of oxidation number2. The order of reactivity of metal from highest to the lowest is Na

Mg Al Zn Fe Pb H Cu Ag. The metal in the left side can reduct the

metal in its right side.

3. The value of E positive shown the reaction is spontaneously.4. Electrolysis of KI solution

In the cathode formed H2(gas bubbles) and OH- The change of FeCl3 with solution of cathode shows that

the solution is base (Fe(OH)3)

I2from anode change amylum become black I2change CHCl3into pink and in anode is polar

Electrolysis of CuSO4solution

In the cathode Cu2+is reducted into Cu C electrode is inert. So, the negative ion will be oxidized

except remaining of oxy acid. Like SO42- the water

(H2O) will be oxidized.

Suggestion :

1. Before doing experiment should be understand about the theory of theexperiment.

2. Be careful to use the material of the experiment.


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5. ReferenceSapardi, Kasmadi. 2012. Kimia Dasar II. Semarang: Unnes

Susilowati, Endang. 2006. The Theory and Application of Chemistry. Solo: PT

Tiga Serangkai Mandiri

Zumdahl, Steven S and Decoste, Donald J. 2007. World of Chemistry. USA :

Houghton Mifflin Company


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6. Questiona. Redox Titration :

1) Cu(s)+ 2AgNO3(aq) Cu(NO3)2(aq)+ 2Ag(s)2) AgCuPbFeZnAlNa

Because the more reactive so that easier to be oxidized

and more difficult to be reducted

3) AgCuHPbFeZnAlNa

b.Electrolysis of KI solution1)Salt bridge contains an electrolyte solution that does not interfere in the

reaction.2)There are many gas bubble in cathode signify that in the solution of was a

flow of electricity and produced H2 gas. A flow of elevtricity was useful

to make a reaction which were not spontaneous be spontaneous.

c. Electrolysis of CuSO41)CuSO4(aq) Cu2+(aq)+ SO42-(aq)

Cathode (-) :Cu2+(aq)+ 2e Cu(s) |x2| 2Cu2+(aq)+ 4e 2Cu(s)

Anode (+) :2H2O(l) 4H+

(aq) + O2(g)+ 4e

Cell reaction : 2Cu2+

(aq)+ 2H2O(l) 2Cu(s)+ 4H+

(aq)+ O2(g)

2)To change the color of solution so the solution of shown by the adding PP.3)CHCl3was phase organic. It couldnt be dissolved4)Because C electrode is inert which can be oxidized by negative ions except

remaining of oxy acid.

electrochemistry.docx

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