# 0.4 Gram equivalent concept  (Page 2/4)

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## Equivalent weight of a base

The valence factor of a base is equal to its acidity. The acidity of a base is equal to furnishable hydroxyl ion (OH-) in its aqueous solution. With this background, we define equivalent weight of a base as :

$\text{Equivalent weight},E=\frac{\text{Molecular weight of base}}{\text{Acidity}}$

Acidity of KOH is 1, whereas acidity of $Ca{\left(OH\right)}_{2}$ is 2. Hence, equivalent weight of KOH is (39 + 16 + 1)/1 = 56/1 = 56. Similarly, equivalent weight of $Ca{\left(OH\right)}_{2}$ is {40 + 2X(16+1)}/2 = 74/2=37.

## Equivalent weight of a compound

The valence factor of a compound depends on the manner a compound is involved in a reaction. The compounds of alkali metal salts and alkaline earth metal salts are, however, constant. These compounds are ionic and they dissociate in ionic components in aqueous solution. In this case, valence factor is equal to numbers of electronic charge on either cation or anion.

$\text{Equivalent weight},E=\frac{\text{Molecular weight of compound}}{\text{Numbers of electronic charge on cation or anion}}$

The numbers of electronic charge on cation of $NaHC{O}_{3}$ is 1. Hence, equivalent weight of $NaHC{O}_{3}$ is (23 + 1 + 12 + 3X16)/1 = 84.

If we look at the defining ratio of equivalent weight of a compound (AB) formed of two radicals (say A and B), then we can rearrange the ratio as :

$\text{Equivalent weight, E}=\frac{\text{Molecular weight of Radical A}}{\text{Numbers of electronic charge}}+\frac{\text{Molecular weight of Radical B}}{\text{Numbers of electronic charge}}$

Thus,

$⇒\text{Equivalent weight of AB}=\text{Equivalent weight of A}+\text{Equivalent weight of B}$

## Equivalent weight of an ion

The valence factor of an ion is equal to numbers of electronic charge on the ion. Therefore, we define equivalent weight of an ion as :

$\text{Equivalent weight},E=\frac{\text{Molecular weight of ion}}{\text{Numbers of electronic charge}}$

The numbers of electronic charge on carbonate ion ( $C{O}_{3}^{2-}$ ) is 2. Hence, equivalent weight of carbonate ion is (12 + 3X16)/1 = 60/2 = 30. Similarly, equivalent weight of aluminum ion ( $A{l}^{3+}$ ) is 27/3 = 9.

## Equivalent weight of an oxidizing or reducing agent

In a redox reaction, one of the reacting entities is oxidizing agent (OA). The other entity is reducing agent (RA). The oxidizer is recipient of electrons, whereas reducer is releaser of electrons. The valence factor for either an oxidizing or reducing agent is equal to the numbers of electrons transferred from one entity to another.

$\text{Equivalent weight},E=\frac{\text{Molecular weight of compound}}{\text{Numbers of electrons transferred in redox reaction}}$

Alternatively,

$\text{Equivalent weight},E=\frac{\text{Molecular weight of compound}}{\text{Change in oxidation number in redox reaction}}$

Potassium dichromate in acidic medium is a strong oxidizer. It means it gains electrons during redox reaction. Potassium dichromate in acidic solution results in :

${K}_{2}C{r}_{2}{O}_{7}+14{H}^{+}+6{e}^{-}\to 2{K}^{+}+2C{r}^{3+}+7{H}_{2}O$

$\text{Equivalent weight of}\phantom{\rule{1em}{0ex}}{K}_{2}C{r}_{2}{O}_{7}=\frac{294.2}{6}=49$

Study of redox reaction is in itself an exclusive and extensive topic. We shall, therefore, discuss redox reaction separately.

## Gram equivalent(geq)

It is equal to mass in grams numerically equal to equivalent weight. If the mass of a chemical entity is “g” grams, then the given mass contains gram equivalents given by :

#### Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
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Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
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Adin Reply
?
Kyle
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biomolecules are e building blocks of every organics and inorganic materials.
Joe
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research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
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what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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characteristics of micro business
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s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
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what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
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for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
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Source:  OpenStax, Stoichiometry. OpenStax CNX. Jul 05, 2008 Download for free at http://cnx.org/content/col10540/1.7
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