Diketahui potensial elektrode zink, tembaga, dan aluminium sebagai berikut. Zn2+(aq)+2e−Al3+(aq)+3e−Cu2+(aq)+2e−​→→→​Zn(s) E∘=−0,76 VAl(s)   E∘=−1,66 VCu(s) E∘=+0,34 V​  Berdasarkan data di atas: a. tuliskan diagram sel Volta yang dapat disusun dari ketiga elektrode tersebut; b. tentukan potensial standar tiap-tiap sel tersebut; c. tuliskan reaksi selnya.

Pertanyaan

Diketahui potensial elektrode zink, tembaga, dan aluminium sebagai berikut.

table attributes columnalign right center left columnspacing 0px end attributes row cell Zn to the power of 2 plus sign open parentheses aq close parentheses and 2 e to the power of minus sign end cell rightwards arrow cell Zn open parentheses s close parentheses space E degree equals minus sign 0 comma 76 space V end cell row cell Al to the power of 3 plus sign open parentheses aq close parentheses and 3 e to the power of minus sign end cell rightwards arrow cell Al open parentheses s close parentheses space space space E degree equals minus sign 1 comma 66 space V end cell row cell Cu to the power of 2 plus sign open parentheses aq close parentheses and 2 e to the power of minus sign end cell rightwards arrow cell Cu open parentheses s close parentheses space E degree equals plus 0 comma 34 space V end cell end table 

Berdasarkan data di atas:

a. tuliskan diagram sel Volta yang dapat disusun dari ketiga elektrode tersebut;

b. tentukan potensial standar tiap-tiap sel tersebut;

c. tuliskan reaksi selnya.

S. Lubis

Master Teacher

Jawaban terverifikasi

Jawaban

diagram sel volta yang mungkin adalah Al bold vertical line Al to the power of bold 3 bold plus sign bold parallel to Zn to the power of bold 2 bold plus sign bold vertical line ZnAl bold vertical line Al to the power of bold 3 bold plus sign bold parallel to Cu to the power of bold 2 bold plus sign bold vertical line CuZn bold vertical line Zn to the power of bold 2 bold plus sign bold parallel to Cu to the power of bold 2 bold plus sign bold vertical line Cu; dengan potensial sel masing-masing +0,90 V; +2,00 V; dan +1,10V. Reaksi selnya: Al bold open parentheses italic s bold close parentheses bold and Zn to the power of bold 2 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold yields Al to the power of bold 3 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold plus Zn bold open parentheses italic s bold close parentheses bold space italic E bold degree subscript bold sel bold equals bold plus bold 0 bold comma bold 90 bold space VAl bold open parentheses italic s bold close parentheses bold and Cu to the power of bold 2 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold yields Al to the power of bold 3 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold plus Cu bold open parentheses italic s bold close parentheses bold space italic E bold degree subscript bold sel bold equals bold plus bold 2 bold comma bold 00 bold space VZn bold open parentheses italic s bold close parentheses bold and Cu to the power of bold 2 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold yields Zn to the power of bold 2 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold plus Cu bold open parentheses italic s bold close parentheses bold space italic E bold degree subscript bold sel bold equals bold plus bold 1 bold comma bold 10 bold space V.

Pembahasan

Sel volta merupakan sel elektrokimia yang menerapkan prinsip perubahan energi kimia menjadi energi listrik. Artinya, reaksi harus terjadi secara spontan. Kespontanan reaksi dapat dilihat dari harga potensial reduksi sel (E degree), jika harganya positif maka reaksi tersebut tergolong spontan.

a. Diagram sel (notasi sel) menunjukkan reaksi oksidasi dan reduksi yang terjadi dipisahkan dengan tanda || yang menunjukkan jembatan garam. Secara umum ditulis sebagai berikut:

Anoda || Katoda

Berdasarkan data, jika Zn dan Al berada dalam satu sistem, maka Zn akan mengalami reaksi reduksi sebab memiliki potensial reduksi lebih besar dari pada Al. Diagram selnya adalah sebagai berikut:

Al vertical line Al to the power of 3 plus sign parallel to Zn to the power of 2 plus sign vertical line Zn 

Jika Al dan Cu berada pada satu sistem, maka Cu akan mengalami reaksi reduksi karena memiliki nilai potensial reduksi lebih besar. Diagram selnya adalah sebagai berikut:

Al vertical line Al to the power of 3 plus sign parallel to Cu to the power of 2 plus sign vertical line Cu 

Jika Zn dan Cu berada pada satu sistem, maka Cu akan mengalami reaksi reduksi karena memiliki nilai potensial reduksi lebih besar. Diagram selnya adalah sebagai berikut:

Zn vertical line Zn to the power of 2 plus sign parallel to Cu to the power of 2 plus sign vertical line Cu 

b. Potensial sel diperoleh dari:

E degree subscript sel equals E degree subscript katoda minus sign E degree subscript anoda 

Sel 1: Al vertical line Al to the power of 3 plus sign parallel to Zn to the power of 2 plus sign vertical line Zn

table attributes columnalign right center left columnspacing 0px end attributes row cell E degree subscript sel end cell equals cell E degree subscript katoda minus sign E degree subscript anoda end cell row blank equals cell negative sign 0 comma 76 space V minus sign left parenthesis minus sign 1 comma 66 space V right parenthesis end cell row blank equals cell plus 0 comma 9 space V end cell end table 

Sel 2: Al vertical line Al to the power of 3 plus sign parallel to Cu to the power of 2 plus sign vertical line Cu

table attributes columnalign right center left columnspacing 0px end attributes row cell E degree subscript sel end cell equals cell E degree subscript katoda minus sign E degree subscript anoda end cell row blank equals cell plus 0 comma 34 space V minus sign left parenthesis minus sign 1 comma 66 space V right parenthesis end cell row blank equals cell plus 2 comma 00 space V end cell end table 

Sel 3: Zn vertical line Zn to the power of 2 plus sign parallel to Cu to the power of 2 plus sign vertical line Cu

table attributes columnalign right center left columnspacing 0px end attributes row cell E degree subscript sel end cell equals cell E degree subscript katoda minus sign E degree subscript anoda end cell row blank equals cell plus 0 comma 34 space V minus sign left parenthesis minus sign 0 comma 76 space V right parenthesis end cell row blank equals cell plus 1 comma 10 space V end cell end table 

c. Reaksi sel:

Sel 1: Al vertical line Al to the power of 3 plus sign parallel to Zn to the power of 2 plus sign vertical line Zn

Reaksi: Al open parentheses italic s close parentheses and Zn to the power of 2 plus sign left parenthesis italic a italic q right parenthesis yields Al to the power of 3 plus sign left parenthesis italic a italic q right parenthesis plus Zn open parentheses italic s close parentheses space E degree subscript sel equals plus 0 comma 90 space V 

Sel 2: Al vertical line Al to the power of 3 plus sign parallel to Cu to the power of 2 plus sign vertical line Cu

Reaksi: Al open parentheses italic s close parentheses and Cu to the power of 2 plus sign left parenthesis italic a italic q right parenthesis yields Al to the power of 3 plus sign left parenthesis italic a italic q right parenthesis plus Cu open parentheses italic s close parentheses space E degree subscript sel equals plus 2 comma 00 space V 

Sel 3: Zn vertical line Zn to the power of 2 plus sign parallel to Cu to the power of 2 plus sign vertical line Cu

Reaksi: Zn open parentheses italic s close parentheses and Cu to the power of 2 plus sign left parenthesis italic a italic q right parenthesis yields Zn to the power of 2 plus sign left parenthesis italic a italic q right parenthesis plus Cu open parentheses italic s close parentheses space E degree subscript sel equals plus 1 comma 10 space V 

Jadi, diagram sel volta yang mungkin adalah Al bold vertical line Al to the power of bold 3 bold plus sign bold parallel to Zn to the power of bold 2 bold plus sign bold vertical line ZnAl bold vertical line Al to the power of bold 3 bold plus sign bold parallel to Cu to the power of bold 2 bold plus sign bold vertical line CuZn bold vertical line Zn to the power of bold 2 bold plus sign bold parallel to Cu to the power of bold 2 bold plus sign bold vertical line Cu; dengan potensial sel masing-masing +0,90 V; +2,00 V; dan +1,10V. Reaksi selnya: Al bold open parentheses italic s bold close parentheses bold and Zn to the power of bold 2 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold yields Al to the power of bold 3 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold plus Zn bold open parentheses italic s bold close parentheses bold space italic E bold degree subscript bold sel bold equals bold plus bold 0 bold comma bold 90 bold space VAl bold open parentheses italic s bold close parentheses bold and Cu to the power of bold 2 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold yields Al to the power of bold 3 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold plus Cu bold open parentheses italic s bold close parentheses bold space italic E bold degree subscript bold sel bold equals bold plus bold 2 bold comma bold 00 bold space VZn bold open parentheses italic s bold close parentheses bold and Cu to the power of bold 2 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold yields Zn to the power of bold 2 bold plus sign bold left parenthesis italic a italic q bold right parenthesis bold plus Cu bold open parentheses italic s bold close parentheses bold space italic E bold degree subscript bold sel bold equals bold plus bold 1 bold comma bold 10 bold space V.

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