Question

7. You decide to construct a zinc/aluminum galvanic cell in which the electrodes are connected by a wire and the solutions are connected with a salt bridge. One electrode consists of an aluminum bar in a 1.0 M solution of aluminum nitrate. The other electrode consists of zinc bar in a 1.0 M solution of zinc nitrate. Draw the complete electrochemical cell diagram and use it to answer the questions that follow. a. Which electrode is the cathode and which is the anode? anode: cathode: b. Label the direction of electron flow on your cell diagram. c. What chemical reactions are occurring at each electrode? reaction at anode: reaction at cathode: d. What is the overall balanced chemical reaction? e. What is the standard cell potential (AE® cell)? f. Express this cell in cell notation.

Answer 1

Galvanic cell is a cell in which cell reaction is spontaneous. If we compare reduction potentials of Al & Zn we found that reduction potential value of Zn is more than the Al. Hence, Zn will acts as a cathode & Al will acts as a anode.

ANSWER : Anode : Aluminium Cathode: Zinc

From given information, we can draw cell diagram as shown below.

CurTEN Salt bridge n electoade A 1-0M2nCNo2 8oluhon Solvtion 1 11 1 111

c) Reaction at anode : Al (s) $\rightarrow$ Al ³⁺ (aq) + 3 e ^-

Reaction at cathode : Zn ²⁺ (aq) + 2 e ^-$\rightarrow$ Zn (s)  

d) Overall balanced equation : 2 Al (s) + 3 Zn ²⁺ (aq) $\rightarrow$ 2  Al ³⁺ (aq) + 3 Zn (s)  

e ) Standard cell potential is calculated as E ⁰ cell = E ⁰ cathode - E ⁰ anode

We have, E ⁰ cathode = - 0.762 V & E ⁰ anode = - 1.677 V

E ⁰ cell = - 0.762 V - ( - 1.677 V ) = 0.915 V

Positive value of standard potential indicates that cell reaction is spontaneous.

f) Cell notation

^- Al (s) I Al ³⁺ ( 1.0 M) II Zn ²⁺ ( 1.00 M ) I Zn (s) ⁺