3) Inert electrodes shall be used if no conductive ones are available,normally Pt,Au are used 4 Pure liquid,solid or gas are next to the inert electrodes seperated by the symbol“|”,“,",or (inert electrode) e.g.（)PtH2(g)lHt HH2(g)Pt(+) (Pt,H2(g)H or:H H2(g),Pt (+ ()(Pt)H2(g)H or:HH(g)(Pt)(+) Negative electrode side Positive electrode side
③ Inert electrodes shall be used if no conductive ones are available, normally Pt, Au are used. ④ Pure liquid, solid or gas are next to the inert electrodes seperated by the symbol “︱”, “,”, or (inert electrode). H+ H2(g) Pt (+) or：H+ |H2(g), Pt (+) or: H+| H2(g) (Pt) (+) Positive electrode side e.g. (-) Pt ⏐H2(g) ⏐H+ (-) Pt, H2(g)⏐H+ (-) (Pt) H2(g) ⏐H+ Negative electrode side
Example:An electrochemical cell has been assembled with the following net reaction.Please write out the cell diagram. 2Fe2+(1.0mol.L)+CL,101325Pa →2Fe3+(0.1mol-L）+2C2.0mol.L） Answer: (+)Cl2(g)+2e=2C1(aq) (-)Fe2*(aq)-e--Fe*(aq) (-)Pt,Fe2+(1.0mol-L-1),Fe3+(0.1mol-L-1)Il Cl (2.0molL-1)|Cl2(101325Pa),Pt(+) Or:(Pt Fe2+(1.0mol-L-1),Fe3+(0.1mol-L-)Cl- (2.0moL-1)|Cl2101325Pa)|Pt(+)
( ) ( ) ( )( ) 3 1 1 2 2 1 2Fe 0.1mol L 2Cl 2.0mol L 2Fe 1.0mol L Cl 101325Pa + − − − + − ⎯⎯→ ⋅ + ⋅ ⋅ + Example: An electrochemical cell has been assembled with the following net reaction. Please write out the cell diagram. Answer ： (+) Cl ( g ) 2e 2Cl (aq ) 2 − − + (-) Fe (aq ) e Fe (aq ) 2 + − 3 + − (-) Pt, Fe2+(1.0mol·L-1), Fe3+ (0.1mol·L-1 ) ‖ Cl - (2.0mol·L-1) ︱Cl 2(101325Pa), Pt (+) Or: (-) Pt︱Fe2+(1.0mol·L-1), Fe3+ (0.1mol·L-1 ) ‖ Cl - (2.0mol·L-1) ︱Cl 2(101325Pa) | Pt (+)
7.2.2 Electrolysis cells and the Faraday's law 1.Electrolysis cells An electrolysis cell is an apparatus in which electrical energy is used to cause a redox reaction to occur. 2.The two Faraday's laws:In 1834,M.Faraday established his quantity theory on electrical process: Faraday's Ist Law of Electrolysis:The mass of a substance altered at an electrode during electrolysis is directly proportional to the quantity of electricity transferred at that electrode.Quantity of electricity refers to the quantity of electrical charge,typically measured in coulomb
* 7.2.2 Electrolysis cells and the Faraday’s law 1.Electrolysis cells An electrolysis cell is an apparatus in which electrical energy is used to cause a redox reaction to occur. 2. The two Faraday’s laws: In 1834, M. Faraday established his quantity theory on electrical process： Faraday's 1st Law of Electrolysis: The mass of a substance altered at an electrode during electrolysis is directly proportional to the quantity of electricity transferred at that electrode. Quantity of electricity refers to the quantity of electrical charge, typically measured in coulomb
Faraday's 2nd Law of Electrolysis: For a given quantity of electricity (electric charge),the mass of an elemental material altered at an electrode is directly proportional to the element's equivalent weight.The equivalent weight of a substance is its molar mass divided by an integer that depends on the reaction undergone by the material e.g.:the mass (m)of deposited Cu at a Cu electrode when Z=2: 63.55 Cu2++2e=Cu gmol。 2 Charge on one mole of electrons: F=1.6021773×1019C×6.022137×1023mo1 =9.648531×104Cmol1 F is called the Faraday constant
e.g.: the mass (m ) of deposited Cu at a Cu electrode when Z = 2: Charge on one mole of electrons： F =1.6021773×10-19C ×6.022137 ×1023mol-1 = 9.648531×104C⋅mol-1 F is called the Faraday constant. g mol 1。 2 63.55 − m ∝ ⋅ Faraday's 2nd Law of Electrolysis: For a given quantity of electricity (electric charge), the mass of an elemental material altered at an electrode is directly proportional to the element's equivalent weight. The equivalent weight of a substance is its molar mass divided by an integer that depends on the reaction undergone by the material Cu2+ + 2e = Cu
27 7.2.3 The measurement of the electro- motive force (EME)of the cell (-）ZnZn2+(1.0moL)‖C2+(1.0moL)Cu(+) Waterfall voltmeter
7.2.3 The measurement of the electromotive force (EMF) of the cell ( − ) Zn Zn (1.0mol⋅L ) Cu (1.0mol⋅L ) Cu ( + ) 2 + − 1 ‖ 2 + − 1 Waterfall voltmeter z7