The copper coulometer is a one application for the copper-copper(II) sulfate electrode. Such a

coulometer A voltameter or coulometer is a scientific instrument used for measuring electric charge (quantity of electricity) through electrolytic action. The SI unit of electric charge is the coulomb. The voltameter should not be confused with a voltmeter ...

consists of two identical copper electrodes immersed in slightly acidic pH-buffered solution of

copper(II) sulfate Copper(II) sulfate, also known as copper sulphate, is an inorganic compound with the chemical formula . It forms hydrates , where ''n'' can range from 1 to 7. The pentahydrate (''n'' = 5), a bright blue crystal, is the most commonly encountered hy ...

. Passing of

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

through the element leads to the anodic

dissolution Dissolution may refer to: Arts and entertainment Books * ''Dissolution'' (''Forgotten Realms'' novel), a 2002 fantasy novel by Richard Lee Byers * ''Dissolution'' (Sansom novel), a 2003 historical novel by C. J. Sansom Music * Dissolution, in mu ...

of the metal on

anode An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...

and simultaneous deposition of

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

ions on the

cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...

. These reactions have 100% efficiency over a wide range of current density.

Calculation

The amount of

electric charge Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...

(quantity of electricity) passed through the cell can easily be determined by measuring the change in mass of either electrode and calculating: :

Q = \frac

, where: *

Q

is the quantity of electricity (coulombs) *

\Delta m

is the mass transported (gm) *

z_

is the charge of the copper ions, equal to +2 *

F

is the

Faraday constant In physical chemistry, the Faraday constant, denoted by the symbol and sometimes stylized as ℱ, is the electric charge per mole of elementary charges. It is named after the English scientist Michael Faraday. Since the 2019 redefinition of S ...

(96485.3383 coulombs per mole) *

M_

is the

atomic weight Relative atomic mass (symbol: ''A''; sometimes abbreviated RAM or r.a.m.), also known by the deprecated synonym atomic weight, is a dimensionless physical quantity defined as the ratio of the average mass of atoms of a chemical element in a giv ...

of copper, equal to 63.546 grams per mole. Although this apparatus is interesting from a theoretical and historical point of view, present-day electronic measurement of time and electric current provide in their multiplication the amount of passed

coulomb The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI). In the present version of the SI it is equal to the electric charge delivered by a 1 ampere constant current in 1 second and to elementary char ...

s much easier, with greater precision, and in a shorter period of time than is possible by weighing the electrodes.

References

Physical chemistry Electroanalytical chemistry devices

Coulometer A voltameter or coulometer is a scientific instrument used for measuring electric charge (quantity of electricity) through electrolytic action. The SI unit of electric charge is the coulomb. The voltameter should not be confused with a voltmeter ...

Coulometers {{physical-chemistry-stub

Calculation

See also

References