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Solutions II
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Methods to calculate Equivalent weights

Shaillee Kaushal is teaching live on Unacademy Plus

Shaillee Kaushal
Faculty in Chemistry with a teaching experience of 14 years. Specialised in teaching for boards and competitions.

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  1. XII-02 Solutions - II

  2. METHODS OF CALCULATING EQUIVALENT MASS Equivalent mass of Acid: Molecular Mass Basicity Basicity no.of replacable. H ions

  3. Equivalent mass of Base Molecular mass Acidity Acidity = no, of repleacable OH-ions KOH-1 B(OH2 Al(OH)3 3 Equivalent mass of salt molecular mass total+ve valency Naci = 1 BaCl2-2 AICI,-3

  4. Equivalent of oxidizing and reducing agents Mol.mass Total electrons gained or lost. For e.g () K2Cr20 electron exchange is 6e (ii) KMnO4-electron exchange is 5e-in acidic medium. = electron exchange is 3e-in basic or neutral medium.

  5. Methods to calculate equivalent weight: Hvdrogen displacement method This method is used for those elements which can evolve hydrogen from acids. Equivalent m Mass of element x 1.008 Mass of hydrogen ass- Mass of element 1.008 volume of in mL of hydrogn displaced 0.00009 Mass of element 11200 volume in mL of hydrogen displaced at NTP

  6. Oxide formation method: Mass of oxygen (Mass of oxide-mass of element) Mass of element Equivalent mas of element = x 8 (Mass of oxide-mass of element) mass of element mass of oxygen

  7. Chloride formation method Mass of chlorine (Mass of chloride - Mass of element) Mass of element quivalent mass Mass of chlorine

  8. Metal to metal displacement method: If E1 and E2 are the equivalent masses of two elements and mi and m2 their respective masses, then m2 E2

  9. Double decomposition method This method depends upon the following factors (a) The mass of the compounds reacted and mass of the product formed are in ratio of their equivalent masses. (b) The equivalent mass of the compound is sum of the equivalent masses of their radicals The equivalent mass of a radical is equal to the formula mass of the radical divided by its charge (c) AB + CD AD + CB Mass of AB Equivalent mass of AB Mass of AD Equivalent mass of AD Eq.mass of A+Eq.mas of B Eq.mass of A+Eq mass of D

  10. Relationship between normality and molaritv: Molarity M olecular mass-Normality Equivalent mass Normality Molecular mass Molarity Equivalent mas:s normality n x Molarity NTxdx10 96 of the solute d-density Eq.wt.of solute (ix) Formality It is used for ionic compounds in which there is no existence of molecule. Mole of ionic compounds is called for mole and molarity as formality