Q.Explain the hydrolysis of different types of salts with the help of examples and comment on the pH of the resulting solutions in each case.

Sodium formate is the salt of a weak acid and a strong base, so its solution is basic (hydrolysis of the formate anion); the standard salt-hydrolysis formula for exactly this weak-acid/strong-base case gives $pH$ in terms of $pK_a$ of the acid and the salt's concentration.

Sodium formate, $HCOONa$, dissociates completely to give $Na^+$ and $HCOO^-$ (formate ion, the conjugate base of the weak acid formic acid, $HCOOH$). The formate ion undergoes hydrolysis in water: $HCOO^- + H_2O \rightleftharpoons HCOOH + OH^-$ making the solution basic (pH $>7$).

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HCOONa is basic, C6H5NH3Cl is acidic, and KCN is basic in aqueous solution.

• HCOONa is the salt of a weak acid (HCOOH, formic acid) and a strong base (NaOH). The formate ion hydrolyses to give a basic solution.
• C6H5NH3Cl (anilinium chloride) is the salt of a weak base (aniline, C6H5NH2) and a strong acid (HCl). The anilinium ion hydrolyses to give an acidic solution. …

A salt hydrolyses only if it comes from a weak acid and/or a weak base; sodium chloride (strong acid + strong base) is the only option among the four whose ions do not react with water.

Salt hydrolysis is the reaction of a salt's constituent ion(s) with water to regenerate the (weak) parent acid or base, altering the solution's pH. Sodium chloride is the salt of a strong acid (HCl) and a strong base (NaOH); neither $Na^+$ nor $Cl^-$ has any appreciable tendency to react with water (their conjugate acid/base, NaOH and HCl, are both fully dissociated strong electrolytes), so NaCl solutions remain neutral — it does not hydrolyse. Sodium formate (from weak formic acid + strong NaOH) hydrolyses to give a basic solution, since the formate ion accepts a proton from …

Methyl orange is used because the HCl-Na2CO3 equivalence point is acidic, not alkaline.

When HCl (a strong acid) is titrated against $Na_2CO_3$ (a salt that behaves as a weak base in water), the overall reaction is:

$Na_2CO_3 + 2HCl \rightarrow 2NaCl + H_2O + CO_2$

At complete neutralisation, the solution contains $CO_2$ dissolved as carbonic acid ($H_2CO_3$), which makes the equivalence-point pH mildly acidic (around 3.5-4), unlike a strong acid-strong base titration where the equivalence point is neutral (pH 7).

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