ELECTROCHEMISTRY

GALVANIC CELL

An electrochemical cell which causes external electric current flow can be created using any two different metals since metals differ in their tendency to lose electrons. Zinc more readily loses electrons than copper, so placing zinc and copper metal in solutions of their salts can cause electrons to flow through an external wire which leads from the zinc to the copper.

As a zinc atom provides the electrons, it becomes a positive ion and goes into aqueous solution, decreasing the mass of the zinc electrode. On the copper side, the two electrons received allow it to convert a copper ion from solution into an uncharged copper atom which deposits on the copper electrode, increasing its mass. The two reactions half reaction are typically written :

Zn(s) → Zn2+(aq) + 2e- (Anode: Oxidation occurs )

Cu2+(aq) + 2e- → Cu(s) (Cathode: Reduction occurs )

The sum of these two half reactions is called the cell reaction and the reaction for this voltaic cell:

Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)

An essential piece of a Galvanic Cell is the salt bridge. The salt bridge serves the vital role of allowing each half-cell's charge to be balanced while preventing the solutions from mixing with each other. Should the solutions be mixed, the reaction will be purely chemical and will not require electrons to flow through the wire -thus, no electricity can be harbored from the cell. Should the charges not be balanced, the anode will have an abundance of positive ions, and the cathode will have an abundance of negative ions. Electrons will not flow with this imbalance. The salt in the salt bridge, however, will ionize and neutralize the charges in each half-cell, allowing the reaction to proceed.

In voltaic cell both oxidation and reduction occurs and this is called as redox reaction. In other words, if one substance is oxidized, then the other must reduced. The electrons formally have to go from one place to another. The substance that makes it possible for another substance to be oxidized is called either the oxidizing agent or the oxidant. The oxidizing agent removes electrons from another substances by acquiring them itself, thus, the oxidizing is reduced. Similarly, a reducing agent, or reductant, is a substance that gives up electrons, thereby causing another substance to be reduced. The reducing agent is therefore oxidized in the process. In both equation Zn act as reducing agent while Ag+

ion act as oxidizing ion.

ENGAGE

BATERRY

You are given the picture as shown below:

1. What do you observe?

2. How electric is produced?

3. What is the process that occurs?

EMPOWER

STEP

1. A voltaic cell uses a spontaneous chemical reaction to generate an electric current. A voltaic cell in a circuit consists of: 

- a negative electrode – anode- a positive electrode – cathode- an electrolyte

2. There are two process happen which is oxidation and reduction occurs.3. Log on the web side and observe the animation to answer the question.

http://www.blackgold.ab.ca/ICT/Division4/Science/Div.%204/Voltaic%20Cells/Voltaic.htm

RESULTS

Voltaic cell between Ag (anode) and Zn (cathode)

The apparatus of voltaic cell

Voltaic cell is started

The movement of ions in both solution

Electrode Zink dissolve in solution become Zn2+

Ag+ ion accept electron and changed to Ag, then deposit on Ag electrode.

Question

1. What is the half reaction of Zn ?

2. What is the half reaction of Ag ?

3. What is the cell reaction of this reaction of voltaic cell ?

4. What happen to Zn and Ag electrode after the process

Answer

1. Zn(s) → Zn2+(aq) + 2e-

2. Ag+ (aq) + e- →Ag (s)

3. Zn(s) → Zn2+(aq) + 2e-

(Ag+ (aq) + e- →Ag (s) ) ×2_______________________________

Zn(s) + 2Ag+ (aq) → Zn2+(aq) + 2Ag (s)

4. Zn electrode are corrosive, because of the ion of Zn dissolved in solution so, the mass of

Zn electrode decrease, but the mass of Ag electrode increase because of ion Ag+ in

solution accept electron from cathode and become Ag.

ENHANCE

The diagram below show the voltaic cell:

Based on the voltaic cell above answer the question below:

1. State the cell reaction of voltaic cell above?

2. In any electrochemical cell, the cathode is the (+) and anode is (-)a. Which electrode is cathode?b. Which electrode is anode?

3. What is the function of salt bridges in voltaic cell?

4. In voltaic cell above which one is act asa. Oxidizing agent?b. Reducing agent?