Quantity of electricity, or charge

Coulometry permits determination of chemical substances by measuring the quantity of electricity required for their conversion to a different oxidation state. The quantity of electricity or charge is measured in Coulombs. (The coulomb is the quantity of charge that is transported in 1 sec... 

The quantity of electricity or charge is measured in units of coulombs (C). A coulomb is the quantity of charge transported in one second by a constant current of one ampere. Thus, for a constant current of I amperes for i seconds, Ihe charge in coulombs Q is given by the expression... 

Quantity of electricity or charge The electrostatic unit of charge, the quantity which when concentrated at a point and placed at unit distance from an equal and similarly concentrated quantity, is repelled with unit force. If the distance is 1cm and force of repulsion 1 dyne and the surrounding medium a vacuum, we have the electrostatic unity of quantity. The electrostatic unit of quantity may be defined as that transferred by electrostatic unit current in unit time. The quantity transferred by 1A in 1 s is the coulomb, the practical unit. The faraday is the electrical charge carried by Ig equivalent. The coulomb = 3 x 109esu. Dimensions... 

Two inventions in the 1740s changed the electrical scene dramatically. One was the frictional machine, which made it possible to generate continuous streams of electricity relatively easily the other was the condenser, or Leyden jar, which made possible the storage and sudden discharge of substantial quantities of electric charge. 

Faraday Constant (F) the quantity of electric charge involved in the passage of one Avagadro number (or one mole) of electrons. The value of F (universal) is 96 485 C mol . ... 

The positive or negative charge (commonly symbohzed by Q or g) on a molecule, radical, or particle resulting from the deficient or excess accumulation of electrons. Electric charge need not be an integer value. The SI unit coulomb (abbreviated C) equals the quantity of electricity transferred by an electric current of 1 ampere over the period of 1 second. 

In writing electron-transfer reactions, we express the quantity of electricity in terms of moles of electrons. One mole of electrons is equivalent to 96,487 coulombs of electrical charge. This quantity of electricity is called the Faraday constant (F), in honor of Michael Faraday, the first pioneer in quantitative electrochemistry. The value ofF can be expressed either as 96,487 coulombs or as 1 faraday. 

Coulometry comprises a set of techniques in which the total charge required (not the current, as in potentiometry) to oxidize or reduce the chemical species of interest is measured. The prime virtue of coulometric techniques is that they link the quantity of substance determined directly to the quantity of electrical charge, and thus expensive and often difficult procedures for standardization or calibration can be minimized or eliminated. 

One coulomb C or one ampere-second is a unit of quantity of electricity (electric charge) required to deposit 0,001118 grams of silver from a solution of silver nitrate regardless of the time during which the current passed through the electrolytic cell. This definition means that a current of one ampere represents a quantity of electricity equivalent to one coulomb per second. 

Coulometry — In 1834 - Faraday described two fundamental laws of - electrolysis. According to Faraday the amount of material deposited or evolved (m) during electrolysis is directly proportional to the current (I) and the time (t), i.e., on the quantity of electricity (amount of charge) (Q) that passes through the solution (first law). The amount of the product depends on the equivalent mass of the substance electrolyzed (second law). 

The colloid, as usually prepared, is electro-positive in character, and may be precipitated from solution by electrolysis, by the addition of small quantities of electrolytes, or by the action of an oppositely charged colloid, such, for example, as (negative) arsemous sulphide, whereby the two electrical charges neutralise each other.7 The smallest quantities of a few electrolytes required to precipitate colloidal ferric hydroxide from solution are given in the following table —8... 

The product of current strength and time is known as the quantity of electricity it has the same dimensions as electric charge. The e.m. unit of charge or quantity of electricity is thus 3 X 10 ° larger than the corre-... 

The e.m. and e.s. units described above are not all of a convenient magnitude for experimental purposes, and so a set of practical units have been defined. The practical unit of current, the ampere, often abbreviated to amp., is one-tenth the e.m. (c.g.s.) unit, and the corresponding unit of charge or quantity of electricity is the coulomb the latter is the quantity of electricity passing when one ampere flows for one second. The practical unit of potential or e.m.f. is the volt, defined as 10 e.m. units. Corresponding to these practical units of current and e.m.f. there is a unit of electrical resistance this is called the ohm, and it is the resistance of a conductor through which a current of one ampere passes when the potential difference between the ends is one volt. With these units of current, e.m.f. and resistance it is possible to write Ohm s law in the form... 

Transference Numbers.—The quantity of electricity qi carried through a certain volume of an electrolytic solution by ions of the tth kind is proportional to the number in unit volume, i.e., to the concentration d in gram-ions or moles per liter, to the charge Zi carried by each ion, and to the mobility w , i.e., the velocity under unit potential gradient (cf. p. 58) thus... 

The mass of a given substance that is produced or consumed at an electrode is proportional to the quantity of electric charge passed through the cell. 

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