Question

Valency factor of Acidic Acid

Answer 1

Explanation:

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For Acids

Acids are the species which furnish H+ ions when dissolved in a solvent. For acids, n-factor is defined as the number of H+ ions replaced by 1 mole of acid in a reaction. Note that the n-factor for acid is not equal to its basicity; i.e. the number of moles of replaceable H+ atoms present in one mole of acid.

For example, n-factor of HCI = 1,

n-factor of HNO3 = 1,

n-factor of H2SO4 = 1 or 2, depending upon extent of reaction it undergoes.

H2SO4 + NaOH → NaHSO4 + H2O

Although one mole of H2SO4 has 2 replaceable H atoms but in this reaction H2SO4 has given only one H+ ion, so its n-factor would be 1.

H2SO4 + 2NaOH → Na2SO4 + 2H2O

The n-factor of H2SO4 in this reaction would be 2.

For Bases :

Bases are the species, which furnish OH– ions when dissolved in a solvent. For bases, n-factor is defined as the number of OH– ions replaced by 1 mole of base in a reaction. Note that n-factor is not equal to its acidity i.e. the number of moles of replaceable OH– ions present in 1 mole of base.

For example,

● n-factor of NaOH = 1

● n-factor of Zn(OH)2 = 1 or 2

● n factor of Ca(OH)2 = 1 or 2

● n factor of AI(OH)3= 1 or 2 or 3

● n factor of NH4(OH) = 1

For Salts :

Salts which react such that no atom undergoes change in oxidation state. The n-factor for such salts is defined as the total moles of cationic/anionic charge replaced in 1 mole of the salt. For the reaction,

2Na3PO4 + 3 BaCI2 → 6 NaCI + Ba3(PO4)2

To get one mole of Ba3(PO4)2, two moles of Na3PO4 are required, which means six moles of Na+ are completely replaced by 3 moles of Ba2+ ions. So, six moles of cationic charge is replaced by 2 moles of Na3PO4, thus each mole of Na3PO4 replaces 3 moles of cationic charge. Hence, n-factor of Na3PO4 in this reaction is 3.

Salts which react in a manner that only one atom undergoes change in oxidation state and goes only in one product. The n-factor of such salts is defined as the number of moles of electrons exchanged (lost or gained) by one mole of the salt.

Let us have a salt AaBb in which oxidation state of A is +x. It changes to a compound, which has atom D in it. The oxidation state of A in AcD be +y.

Aa+x Bb → Ac+yD

The n-factor of AaBb is calculated as

n = |ax – ay|

For example, let us calculate the n-factor KMnO4 for the given chemical change.