## Search This Blog

**SALT HYDROLYSIS:**. Show all posts

**SALT HYDROLYSIS:**. Show all posts

## Sunday, September 10, 2023

## Saturday, September 26, 2020

### What are DOUBLE SALTS ?

**DOUBLE SALTS:**

**Mohar’s salt-**FeSO

_{4}(NH

_{4})

_{2}SO

_{4}.6H

_{2}O (Ferrous ammonium sulphate)

**Alum’s**- K

_{2}SO

_{4}Al

_{2}(SO4)

_{3}. 24H

_{2}O (Potassium ammonium sulphate)

**Karnalite-**KCl.MgCl

_{2.}6 (H

_{2}O)

**Dolomite-**CaCO

_{3}.MgCO

_{3}or CaMg (CO

_{3})

_{2}

## Sunday, November 4, 2018

### [5] POLYVALENT ION HYDROLYSIS:

**(1) POLY ANION HYDROLYSIS:**

**(Poly acidic base):**

_{4}

^{-3 }(n=3) , C

_{2}O

_{4}

^{-2 }(n=2), S

^{-2 }(n=2) , N

^{-3}(n=3) etc.

**DISSOCIATION CONSTANT OF PHOSPHORIC ACID:**

**Step-1**

**HYDROLYSIS OF ANION (PO**

_{4}^{-3}):_{1}>>Ka

_{2}>>Ka

_{3,}hence

_{ }x

_{ }>>y>>Z so y and z can be neglected with respect to x

**Special Case (1):**

**Special Case (2)****Step-2**

_{1}>>Ka

_{2}>>Ka

_{3 }hence

_{ }x>>y>>Z So y and z can be neglected with respect to x and the x present in denominator and numerator both are cancelled .

**Step-3**

_{1}>>Ka

_{2}>>Ka

_{3 }hence

_{ }x>> y>>Z So y and z present in numerator can be neglected with respect to x and the z present in denominator is also neglected with respect to y.

**(2) POLY CATION HYDROLYSIS:**

**(Poly basic acid):**

For example Ca

^{+2}, Fe

^{+3}, Al

^{+3 }, Mn

^{+2}, Cd

^{+2 }, Zn

^{+3}etc

ILLUSTRATIVE EXAMPLE:

Calculate pH and concentration of all species in 0.1 M solution of FeCl

_{3}given Fe(OH)

_{3 }have Kb

_{1}=10

^{-3}, Kb

_{2}=10

^{-7}and Kb

_{3}=10

^{-12}.

**SOLUTION:**

^{ }Fe

^{+3 }àundergo hydrolysis while, Cl

^{- }à do not under goes hydrolysis.

^{}

_{1}>>Kb

_{2}>>Kb

_{3 }so

_{ }x>>Y and Y>>Z

**HYDROLYSIS OF FeCl**

_{3}:_{}_{1}>>Ka

_{2}>>Ka

_{3 }, hence

_{ }x>>y>>Z So y and z can be neglected with respect to x

**TITRATION BASED POLYVALENT ION HYDROLYSIS:**

**(1) TITRATION OF Na**

_{2}CO_{3}Vs HCl:**(2) TITRATION OF NA**

_{3}PO_{4}Vs HCl:

**(1) TITRATION OF Na**

_{2}CO_{3}Vs HCl:

**ILLUSTRATIVE EXAMPLE:**

The following volume of 0.1M HCl Solution is added to the in20 ml 0.1M Na

_{2}CO

_{3}Solution the pH of resulting solution in each case.

(H

_{2}CO

_{3}, Ka

_{1}= 4×10

^{-6}, Ka

_{2}= 5×10

^{-11})

**(1)**0.0 ml (No HCl added)

**(2)**10 ml HCl is added

**(3)**20 ml HCl is added

**(4)**30 ml HCl is added

**(5)**40 ml HCl is added

## Saturday, November 3, 2018

### Amphoteric salts hydrolysis:

Example
of amphoteric salts NaHS, NaHCO_{3}, Na_{2}HPO_{4},
NaH_{2}PO_{4}

**(A) **HCO3- act as conjugate acid as well as conjugate
base:

_{}

Both
reaction will support each other extent of hydrolysis and extent of
dissociation is same.

**(B)** Here H_{2}PO_{4}^{-} and HPO_{4}^{-2}
are amphoteric anions. The pH of amphoteric salts anions is independent of
concentration of salts.

Here HPO_{4}^{-2 }is conjugate base of H_{2}PO_{4}^{-}
and H_{3}PO_{4} is conjugate acid of H_{2}PO_{4}^{-}Similarly PO_{4}^{-3} is conjugate base
of HPO_{4}^{-2 }and H_{2}PO_{4}^{-1} is
conjugate acid of HPO_{4}^{-2}

When these salts are dissolved in water [H_{3}O+]
concentration can be determined as;

**ILLUSTRATIVE
EXAMPLE: **Calculate pH
of solution of

(1) 100 ml
0.1M H_{3}PO_{4} + 100 ml 0.1M NaOH.

(2) 100 ml
0.1M H_{3}PO_{4} + 200 ml 0.1M NaOH.

(3) 100 ml
0.1M H_{3}PO_{4} + 300 ml 0.1M NaOH.

(4) 100 ml
0.1M H_{3}PO_{4} + 400 ml 0.1M NaOH.

## Wednesday, October 31, 2018

### [3] CATIONIC AS WELL AS ANIONIC HYDROLYSIS:

^{+}& OH

^{–}and rearranging,

__Now, we calculate the pH of the solution as:__

**ILLUSTRATIVE EXAMPLE (1)**: calculate the pH of 0.2 M NH4CN Solution. ( Given Ka HCN is 3x10-10 and kb NH4OH is 2.0x10-5)

**ILLUSTRATIVE EXAMPLE (2):**

**ILLUSTRATIVE EXAMPLE (3):**

**ILLUSTRATIVE EXAMPLE (4):**

**ILLUSTRATIVE EXAMPLE (5):**

### [2] CATIONIC SALT HYDROLYSIS:

**(2) CATIONIC HYDROLYSIS OR ACIDIC SALTS HYDROLYSIS:**

**(Salt of a Weak Base and a Strong Acid)**

_{4}OH. Therefore the salt would be NH

_{4}Cl.

_{4}Cl completely dissociates into NH

_{4}

^{+}and Cl

^{–}ions.

^{+}ions and Cl

^{–}ions.

_{4}OH and H

^{+}are being produced. This implies that the solution is acidic

**To calculate pH**,

^{–}and rearranging,

### [1] ANIONIC SALT HYDROLYSIS:

**(1) NEUTRAL SALTS:**

**(**Salts of strong acids and strong bases)

**(2) ALKALINE SALTS**:(Salts of weak acids and strong bases)

**(3) ACIDIC SALTS:**(Salts of weak bases and strong acids)

**(4)**Salts of weak acids and weak bases

#### (1) ANIONIC HYDROLYSIS OR ALKALINE SALTS HYDROLYSIS:

#####
(Salt of a Weak Acid and Strong Base)

_{3}COOH) and add to it the same amount of a strong base (NaOH). They will react to produce CH

_{3}COONa.

_{3}COONa being a strong electrolyte, completely dissociates into its constituent ions.

**Now, the ions produced would react with H**

_{2}O. This process is called hydrolysis^{+}and OH

^{–}ions.

^{+}on both the sides,

**ions coming from strong bases do not get hydrolysed.**We should note here that the solution will be basic. This is because the amount of CH

_{3}COOH produced and OH

^{–}produced are equal. But CH

_{3}COOH will not completely dissociate to give H

^{+}ions. Therefore [OH

^{–}] ions will be greater than [H

^{+}] ions.

_{c}is given a new symbol, K

_{h}

^{+}] of the solution, then

**CASE (1**): If a is very much less than 1, then 1-a= 1 this approximation valid when C/Kh is greater than 100”

**CASE (2):**If C/Kh is lower than 100 than calculate h by formation of quadratic equation.

**ILLUSTRATIVE EXAMPLE (1):**A 0.0258 M solution of the sodium salt, NaH of the weak monoprotic acid, HA has a pH of 9.65. Calculate Ka of the acid AH.

**ILLUSTRATIVE EXAMPLE (2):**What is the pH of 0.10 M CH

_{3}COONa solution. Hydrolysis constant of sodium acetate is 5.6 × 10

^{-10 }

**?**

**SOLUTION:**Hydrolysis of the salt may be represented as

**ILLUSTRATIVE EXAMPLE (3):**Calculate pH of

**1.0 x 10**

^{-3 }M Sodium phenolate (Na

^{+}O

^{-}C

_{6}H

_{5}) Ka for C

_{6}H

_{5}OH is 1.0 x10

^{-10 .}

**SOLUTION: (**Ans- pH=10.43)

**(2) CATIONIC HYDROLYSIS OR**

**ACIDIC SALTS HYDROLYSIS:**