ENERGY DEVICES (Mod 4) - ELECTROCHEMICAL CELL

Question 1

Define ELECTROCHEMICAL CELL

Answer 1

• a device that is used to generate electricity from a spontaneous redox reaction
• a device that uses electricity to drive a non spontaneous redox reaction

Question 2

What does an electrochemical cell CONSIST OF?

Answer 2

1. TWO ELECTRODES - electronic conductors
2. ELECTROLYTE - ionic conductor
3. COPPER WIRING - electron conductor used to link the electrodes is often a metal wire

Question 3

TYPES of ELECTROCHEMICSL CELLS

Answer 3

1. GALVANIC / VOLTAIC CELL - converts energy released by a spontaneous chemical reaction to electrical energy (ΔG = -ve)
2. ELECTROLYTIC CELL - consumes electrical energy from an external source to drive a non spontaneous reaction (ΔG = +ve)

Question 4

1. Define GALVANIC CELL

Answer 4

A galvanic cell uses the energy released during a spontaneous redox reaction (ΔG < 0) to generate electricity.

Question 5

galvanic cell is also called ___?

Answer 5

voltaic cell

Question 6

why is galvanic cell also called voltaic cell

Answer 6

This type of electrochemical cell is also called a voltaic cell after its inventor, the Italian physicist Alessandro Volta.

Question 7

what occurs at anode

Answer 7

Anode is written on the left-hand side &raquo_space; oxidation occurs

Question 8

what occurs at cathode

Answer 8

Cathode is written on the right-hand side &raquo_space; reduction occurs

Question 9

2. Define DANIEL CELL

Question 10

daniel cell was invented by

Answer 10

Invented by British chemist John Frederic Daniell.

Question 11

daniel cell was invented by

Answer 11

Invented by British chemist John Frederic Daniell.

Question 12

Each electrode is referred to as ____

Answer 12

half cell

Question 13

half cells (electrodes) in daniel cell are connected through

Answer 13

connected through a salt bridge

Question 14

functions of salt bride

Answer 14

• Salt bridge: KCl or NH4Cl in a gelatine form
• Maintains the charge balance in the two half cells
• Minimizes or eliminates the liquid junction potential

Question 15

define EMF of electrochemical cell

Question 16

describe The Electrolysis of Molten NaCl

Answer 16

Here Na+ ions gain electrons and are reduced to Na at the cathode.
As Na+ ions near the cathode are depleted, additional Na+ ions migrate in.
Similarly, there is net movement of Cl- ions to the anode where they are oxidized to Cl2.

Question 17

Electrolysis is performed at what temp

Answer 17

801 °C

Question 18

what are the electrodes used in The Electrolysis of Molten NaCl

Answer 18

Here inert electrodes are used

Question 19

chemical equations for The Electrolysis of Molten NaCl

Answer 19

Cathode: 2 Na+ (l) + 2 e- → 2 Na (l)
Anode: 2 Cl ̶ (l) → Cl2 (g) + 2 e-
Overall: 2 NaCl (l) → 2 Na (l) + Cl2 (g)

Question 20

describe Electrolytic Decomposition of Water

Answer 20

A pair of inert electrodes are dipped into the solution and applying a voltage between them results in the rapid evolution of bubbles of H2and O2.
= toh water decompose ho aya into hydroen and oxyen molecules

Question 21

why is a small amount of an ionic solute (such as H2SO4or Na2SO4) is added to pure water in Electrolytic Decomposition of Water

Answer 21

Due to very poor electrical conductivity of pure water, a small amount of an ionic solute (such as H2SO4or Na2SO4) is added to increase its electrical conductivity.

Question 22

Electrolytic Decomposition of Water chemical equations

Answer 22

The electrolytes are chosen such a way that the ions that are harder to oxidize or reduce than water:
Cathode: 4 H+(aq) + 4 e- → 2 H2(g)
Anode: 2 H2O → O2(g) + 4 H+ + 4 e-
Overall: 2 H2O → O2(g) + 2 H2(g)

Question 23

describe Electroplating

Answer 23

Uses electrolysis to deposit a thin layer of one metal on another metal to improve beauty or resistance to corrosion.

Question 24

electroplatin was discovered by

Answer 24

Electroplating was first discovered by Luigi Brugnatelli in 1805 through using the electrode position process for the electroplating of gold.

Question 25

examples of electro platin

Answer 25

Both ferrous and non-ferrous metals are plated with Ni, Cr, Cu, Zn, Pb, Al, Ag, Au, Sn etc.

Question 26

describe process of Electroplating

Answer 26

• The base metal to be plated is made cathode of an electrolytic cell.
• The anode is either made of the coating metal itself or an inert material of good electrical conductivity.
• A water-soluble salt of the plating metal is used as electrolyte.

Question 27

why are non-participating electrolytes, such as, Na2SO4 added to the bath solution?

Answer 27

Often non-participating electrolytes, such as, Na2SO4, are added to the bath solution to increase the conductivity of the medium.

Question 28

copper platin